Thursday, April 20, 2017

Draft of Detecting an Observable Decline in Serial Homicide: Have We Banished the Devil from the Details?

No greater assumptions are made within the realm of serial homicide research than the overstated impact these offenders have on rates of violence in America. Spotlighting the proportion of the “dark figure of crime” serial murderers occupy is consumed by supposition and a myriad of problems, foremost among them the discordance in expert opinions on the relatedness between missing and unidentified persons, unsolved murders, no-body homicides, equivocal and mislabeled deaths, the “missing missing”, and the unclaimed dead. Sisyphean endeavors to address the incidence of serial homicide offenders have stalled since the 1990s (Hinch & Hepburn, 1998; Kiger, 1990; Mott, 1999; Schlesinger, 2001; Stote & Standing, 1995) replaced by scholars unaware even of the number of serial killers active across history (Wiest, 2011). The confusion surrounding recent homicide rate increases (Asher, 2017; Economist Data Team, 2017; Park & Katz 2016; Winkley, 2017) and missing persons (Davis & Hermann, 2017) around the United States (US) has sustained reliance on anecdotes, continuing a legacy of myths and stereotypes to inform on the topic of trends in serial murder. These knowledge gaps loom large over empirical analysis and impede further study of the phenomenon. This review aims to examine the observed decline in serial homicide by first investigating the plausibility of reaching a true prevalence of the phenomenon, then uncovering what proportion of the “dark figure” they occupy and finally probing the likelihood that these offenders are responsible for the rise in unresolved homicides by addressing the myths surrounding their capabilities.

While current Attorney General Jeff Sessions has called a recent “surge” in murder rates a “dangerous permanent trend” (Bump, 2017), scholars outside of the serial homicide research arena (Pinker, 2012; Roser, 2017) agree that homicidal violence has been declining for decades. If American society has been enjoying a historic period of abatement, why, then, are atypical homicide researchers insistent that serial homicide rates have been steadily increasing? Use of specific phraseology and heavy reliance on vagaries to explain the pervasiveness of offenders during the early 1980s drew attention towards the phenomenon of serial homicide by classifying these crimes as “stranger murders” (Reid, 2017a), an action that purposefully instilled fear and promoted terror. The lack of consensus on prevalence among researchers and no official statistics regarding serial murderers in the US (McNamara & Morton, 2004) continues to confuse scholars and has fortified the stance of those that believe serial homicide is not in decline. Consider that detectives at the Tacoma Police Department in Washington are reviewing all unresolved homicide cases from 1970 to 2017 involving female victims aged 14-40 known to be involved in prostitution (Lindsey Wade, personal communication, 20 December 2016), a total of 80 individuals over a span of nearly 50 years. Without confirmation that serial murderers are responsible for any of these homicides it is difficult to contrast these happenings with a popular notion that the Northwest generates more serial murderers than other geographic regions (Bartlett, 2016).

Stote and Standing (1995) found no sign of a suddenly emerging social psychology after correcting rates for population increases when investigating the supposed epidemic of serial homicide. Still, the belief that many successful killers have gone undetected endures among detractors of the decline theorists (Giannangelo, 2012) bolstered by relentless coverage of abysmal homicide clearance rates (Gramlich, 2017), various issues facing detectives (Henderson, Tracy, Parascandola & Mcshane, 2016; Ransom, 2016; Kelly, Lowery & Rich, 2016) staggering reports of the sheer number of unresolved homicides in the US (Stein, 2017) reference to the latter as a national crisis (Adcock, 2017) and speculative estimates from serial homicide researchers without access to good data (Lester, 1995). Some believe there to be two active serial killers in every major city in the US[i] (Phelps, 2013) while Miller (2014) builds upon those outrageous estimates by stating that between 200 and 500 serial murderers kill 2,000 to 3,500 victims a year allotting 10% of all murders in the US to their activities. While Miller (2014) is undecided if this ostensible increase in the number of serial killers captured and recorded should be attributed to either an actual surge in the rate or to better profiling and crime-solving techniques, Racine (2015) and Moss (2015) consider the current state of serial homicide research and determined that a wide range of factors influence frequency estimates. Inaccuracies will continue to abound due to the uneven access that researchers maintain to databases that catalog known and unresolved serial homicide series combined with continued acceptance of disciplinary thinking (Yaksic, 2017).

Mindhunter, the upcoming Netflix original series (Trenholm, 2017), will undoubtedly contribute to a resurgence of interest in the original study of 25 serial murderers conducted in the late 1980s by agents of the Federal Bureau of Investigation (FBI) (Beasley, 2004) from which the majority of modern day myths about serial homicide arose. While McIntire (2016) uses data visualizations to illustrate that the profile of a serial killer is more nuanced than Hollywood depictions, Schlesinger (2001) concludes that those early efforts to understand these offenders led to the origin of a popular and still unrefuted theory that draws a concomitant link between falling clearance rates for homicide and an increase in serial murders, known then as “homicides with unknown motives” or “stranger murders”. Hinch and Hepburn (1998) note that it is inaccurate to attribute most stranger or unknown homicides to serial murder, especially if done because of problems with quantification such as incomplete and unreliable data. For example, admitting as a limitation that data sources - such as the FBI’s Supplemental Homicide Reports (SHR) – exist in an incomplete format has invited imaginative conjecture about the contents of the missing records, granting researchers permission to extrapolate the handful of serial offenders discovered yearly tenfold and beyond. Quinet and Nunn (2014) negate the ongoing myth that unresolved homicides are disproportionately stranger homicides. The results of their research indicate that decreased homicide clearance rates are not due to increased stranger homicides, confident that the hidden proportion of unknown offender homicides that are stranger homicides has not increased. Pastia, Davies, & Wu (2017) found that incident characteristics - notably drug or gang involvement - largely determined differences in clearance times among demographic variables. Sarteschi (2016) reminds researchers that this concealed population inhabits the “dark figure of crime” invisibly and maintains an ever-present command over the advancement of the study of serial murder.

Many credit these clandestine killers with scores of both unknown perpetrator homicides and the deaths of missing persons (Homant & Kennedy, 2009). The state of missing persons in the US has been referred to as a “silent mass disaster” (Ritter, 2007) but the grand majority of records entered into the FBI’s National Crime Information Center (NCIC) database in 2014 (635,155) were cleared at a rate of 99.87 percent with 788 records remaining (Yoder, 2016). Because timely and accurate data on the number of missing persons that are victims of homicide is nonexistent, the percentage of missing persons felled by serial murderers cannot be known. Accounting for this limitation, Shanafelt and Pino (2013) propose that we examine serial killing in a larger context. Researchers should consider, for example, the rarity for serial murders to occur without at least some of the victim’s bodies being discovered within a relatively short period of time following the crime (LePard, Demers, Langan, & Rossmo, 2015). It is also exceedingly rare for the results of a serial murderer’s confession to contain references to unclaimed bodies or for offenders to be the subject of “no-body” prosecutions (Tad DiBiase, personal communication, 5 December 2016) meaning that the victims of serial killers are usually located, then processed by medical examiners. More often than not, missing persons are eventually found unharmed with a small minority reaching the rank of “critical missing” (Jones, 2017). Given this information, it is irresponsible to conclude that any significant majority of missing or unidentified persons are the result of serial homicide activity.

Definitional issues complicate serial killing incidence rates as researchers focus too narrowly on minutiae regarding components such as victim thresholds, time intervals and evidence of linkages between homicides (Homant & Kennedy, 2009). The singular focus on terminology (Reid, 2017b) and an inconsistent application of rigor to academic inquiries (Dowden, 2005; Levin & Fox, 2017) has resulted in interrupted progress and an imbalance in the advancement of descriptions which have outpaced empirical data collection. DeLisi (2015) agrees, suggesting that tension regarding the criminal careers of serial murderers – comparing those that manage to avoid accumulating criminal charges to those mixing serial homicide into a versatile history of offending – distracts researchers from answering questions empirically. Normal personalities are thought to be incapable of serial murder as mythmaking has fallaciously transformed the concept (Homant & Kennedy, 2009; Jenkins, 2002) beyond being committed by those harboring complex idiosyncratic combinations of processes that incorporate emotions, feelings, memories, intentions, fantasies, cultural schema and plans into a multifaceted whole (Shanafelt & Pino, 2013) while exposed to elements of US culture including values of individualism, competition, recognition and personal achievement (DeFronzo, 2007; Wiest, 2016). One byproduct of personifying the serial murderer is a reduction of the victim threshold, a maneuver interpreted as artificially expanding the boundaries for inclusion (Fridel & Fox, 2017) by accommodating offenders whose crimes fall short of earning categorization as “serial”. While this tactic redefines the very nature of the ‘serial killer problem’ and makes it appear more significant (Hodgkinson, 2016), many people - aside from serial killers - have gotten away with murder (Sarteschi, 2016).

True crime authors advance the timeworn sentiment that all killers are multiple murders merely stripped of means and opportunity (M. William Phelps, personal communication, 14 April 2016). Although admissions by apprehended killers and forensic linkages often reveal their complicity in singular, on-off homicides, death at the hands of a serial murderer is often probed as the first probability as in recent panics along Cleveland’s East 93rd Street (Ferrise, 2017; Goldenberg, 2017; Horansky, 2017), New England jogging paths (Williams, 2016), waterways (Herzog, 2016; Rocheleau, 2017) and a northern Indiana trail (Paul, 2017). Exposure to high profile cases has effected an over-reliance by law enforcement organizations (LEOs) on offender profiling as the ‘Law of the Instrument’ in the endless hunt for what are perceived to be ever-present serial murderers. While this misallocation of resources sometimes comes at the detriment of future victims, the accelerated adoption of this protocol starkly contrasts a time period when LEOs waited for an investigative “tipping point” before taking conceptual leaps in entertaining theories pertaining to serial murder (LePard et al., 2015). The haphazard juxtaposition of victimological characteristics[1] can sometimes be indicative of serial murder activity but analyzing these measured groupings together, a consideration once deemed unconventional, can be a Doctrine of Chances and cause police detectives (Augenstein, 2017; Lohr, 2016a), citizen sleuths (Thomas, 2017), journalists (Dissell, 2017; Guenthner, 2017) and family members (Anthony, 2015) to draw non-existent parallels between cases based only on slight similarities such as comparable geography, being felled on the same day of the month, or dates that are equal to demonic numbers (Giacalone, 2017). Although most offenders that fit a certain deviant profile (Lohr, 2016b) are not serial murderers, LEOs fear that any lack of vigilance on their part could result in monumental failures as seen by Project KARE (McClearn, 2017).

Those bereft of the “golden age” of serial killers (Reid, 2017a) posit theories of forensically aware murderers with superior intellects and cunning abilities that obtain highly specialized training from television programs delivering instructions on apprehension avoidance tactics. These postulations run contrary to a reported statistical decrease in prolific murderers (those killing six or more victims) (Aamodt, Fox, Hickey, Hinch, Labuschagne, Levin, McClellan, Nelson, Newton, Quinet, Steiger, White, & Yaksic, 2016) and results from a sample of cases provided by Morton, Tillman and Gaines (2014) where offenders took no precautions to disguise their identity or avoid leaving physical evidence in 58.5% of the cases, took no action to alter crime scenes in 44.6% of the cases, destroyed or removed evidence from the crime scenes in only 36.3% of the cases and cleaned the crime scene in 15.2% of the cases. The argument that other serial murderers are expertly trolling the countryside free of intervention is strengthened because the capture of some killers result from chance LEO encounters, such as Alaska’s James Dale Ritchie (Klint, 2016), and a failure to ameliorate the extent of the serial homicide offender’s presence. Experts provide commentary on active investigations directly or indirectly promoting the likelihood of discovering additional victims and touting nonexistent case linkages that is vague, baseless, speculative and oftentimes misleading (Harris, 2016Homan, 2015; Mazzola, 2017; Smith, 2016; Ward & Shehade, 2016).

Not much has been accomplished in the area of serial homicide offender prevalence since Cavanagh’s (1993) work on experimental procedures in estimation with the first anecdotal (The Practicality of CIA in the 21st Century, Survey, 14 March, 2005), academic (Quinet, 2011) and journalistic (Beam, 2011) mentions of a decline[2] in serial homicide arriving at the beginning of this millennium. Potential reasons for the observed decline have since been introduced (Fox & Levin, 2014; Yaksic, 2013, 2015) to the discontent of those opposed to the notion that serial homicide is decreasing. Detractors imply that introducing an idea of this nature is dangerous in its adverse impact on the future success of grant proposals and book profits suggesting that any observed decline in serial homicide is the result of a dearth of information and diminished interest from LEOs and the community in the once enthralling phenomenon. After all, a decrease in serial homicide stands in opposition to the infallible, adaptable and successful serial killer, a heavily advanced construct that allowed LEOs to attribute their lack of results in resolving homicides to being outmatched by criminals with superior abilities. Those armed with faulty statistics and overactive imaginations are persistent and impervious to efforts to intercede with facts derived from data, a frontier perhaps unsuited to a field built and funded by a reliance on overblown statistics. Quinet (2011) calls the reduction in detected cases of serial murder by decade “dramatic” and dispels the notion that a paucity of information has negatively affected researcher’s ability to assemble the data by noting that media coverage has increased to match the public interest. Levin and Fox (2017) consider the collective impact of unresolved and undetected homicides alongside the methodological caveats concerning the completeness of available data, improvements to data accessibility, increased quality of record keeping and awareness by LEOs and interest by the general public on serial homicide offenders concluding that the occurrence of serial homicide has diminished over the past decade or two.

Serial homicide does appear to be increasing when reflecting on news regarding Gary Sampson (Valencia, 2016), Michael Monert (Fraley, 2016), Steven Gordon (Goffard, 2016), Aeman Presley (WSBTV Staff, 2017), Anthony Kirkland (WKRC Staff, 2016), Stanley Adams (Simeon, 2017), David Ray Contreras (Patch Staff, 2017), Kwauhuru Govan (Weill, 2017), Samuel Little (Kim, 2014), and Clifton Bloomfield (Associated Press, 2016) coupled with renewed interest in longstanding dormant serial homicide series - the Original Nightstalker, Storyville Slayer, Colonial Parkway Killer and the Allenstown Barrel Bodies - from wide ranging areas of the country - West Mesa, Daytona Beach, Long Island, Jefferson Davis Parish and Atlantic City. An underacknowledged caveat regarding these cases, and the careers of serial homicide offenders in general, is their length which oftentimes spans many years, even decades. Because the age of unresolved homicides in LEO files is usually more than five years (depending on how LEOs define these cases) it is deceptive to count the resolution of these types of homicides among the logs of their clearance year – rather than when the crimes were committed – as it inflates serial murder’s contribution to end of year rates, further confusing efforts to establish an accurate and timely snapshot of offending. The practice of LEOs reviewing unresolved homicides upon the discovery of suspected serial murderers bolsters the belief that additional killings and crime rate increases can consistently be attributed to them rather than exploring other explanations such as the more plausible effects of border offenses (Sean Holstege, personal communication, 16 November 2016), human trafficking (Department of Justice, 2017) or gang violence (Hellgren, 2017; Wang, 2016).

Our general lack of knowledge about the amount of serial murderers in modern society was brought to the forefront by The Killing Season, a docu-series that aired on the Arts and Entertainment network (Yandolino, 2016). In advocating for the notion that serial homicide is increasing, the documentarians married three separate approaches: an algorithm created by the Murder Accountability Project (MAP) (Hargrove, Witzig, Icove, Harry, Arntfield, Yaksic, Lang, & Wolf, 2017), tabulation work done by the FBI’s Violent Criminal Apprehension Program (ViCAP) Highway Serial Killings Initiative (HSKI) (Newsweek Staff, 2011) and the Gone Girls profile (Warner, 2016). MAP’s algorithm pinpoints clusters of supposed serial homicide activity by utilizing the FBI’s storied SHR to build the truest count of unsolved homicides in the US while the HSKI is an effort led by the FBI’s ViCAP analysts to index the number of unexplained deaths occurring on or near major highways in the US. Given the enormous scope of these missions, both MAP and the HSKI depend on a mixture of the Gone Girls profile and the ‘Doctrine of Chances’, tallying two cases as related if even the remotest similarities are shared. This flawed methodology may be empirically unsound as it overemphasizes the conjunctiveness of parameters with little value if considered separately. Efforts by both MAP and HSKI served to enhance the television narrative but also erroneously furthered the premise that hundreds of serial murderers are currently roaming the US unabated, “more than in our nightmares” (Romano, 2016). MAP operates under the dual assumptions that uncaught offenders will inevitably kill again using identical methods of death[3] and that most cities retain a few active serial murderers (Kolker, 2017). These assertions seemingly echo sentiments put forth in exaggerated claims related to jogger abductions (Hansen, 2016) and murders staged as suicides (Augenstein, 2016).

Notwithstanding the importance of both the MAP and HSKI initiatives, The Killing Season induced hysteria by inflating the threat serial murderers pose in modern society. For one, the premise of the forecasting methods utilized by MAP was trained against the Green River Killer, notorious for a remarkably uncommon use of clustering victims in tight geographic spaces. It is misleading to feature a program like the HSKI that advertises 450 suspected offenders as some unknown percentage of these murderers would be ‘one-off’ killers given the publicized victim count of 750 deaths. Because a victim’s death must be paired with at least one other individual to be counted as part of a series – as noted by alterations to the FBI’s serial murder definition (Morton & Hilts, 2008) – the victim count should reach at least 900 if each offender killed at least twice. According to the FBI’s public website (Department of Justice, 2016), the program has functioned for twelve years and identified an extra 250 more victims and offenders since its inception – an annual growth rate of four percent. The addition of these 63 victims to yearly victim indexes would be unnerving but since timelines related to the 450 potential suspects actually span back four decades (Terri Turner, personal communication, 15 December 2016) the final estimation is more in line with the discovery of an additional 19 victims a year. Efforts to link homicide victims to data points in the HSKI have been unsuccessful (Pacheco, 2010). Unaware that it is exceedingly unlikely that the number of active serial murderers is growing, at least one chief of police has crafted a readiness plan calling for every law enforcement agency in the US to be prepared for the appearance of a serial murderer in their community (Andreu, 2017).

It was necessary to examine the impact serial murderers may be having on rates of resolved and unresolved homicides because LEOs have demonstrated that clearance rates have been improved after implementing community policing tactics to solve homicides, a process occurring independent of the search for serial homicide offenders or a focus on addressing unresolved homicides. Proponents of the theory that serial homicide is increasing have distorted the missions of both MAP and the HSKI without acknowledging that such exploitation borders on purposeful obfuscation usually to obtain additional funding for related programs. An exploratory evaluation was conducted to counter these inaccuracies using a mixed methods approach consisting of empirical analysis of data on apprehended serial murderers, qualitative interviews of 35 thought leaders and subject matter experts, frequency analyses of known, longstanding unresolved serial homicide series and a review of unresolved homicides from a sample of 19 states.

Into the Known: Exploring an Observed Decline Among Resolved Serial Homicide Series

The data used in this research is from the Consolidated Serial Homicide Offender Database (CSHOD) (Aamodt et al., 2016), consisting of 4,007 serial killers. For the purposes of the CSHOD, a serial killer has killed at least two people in separate events. Although the data set includes international serial killers, all non-US killers and those who operated in multiple countries including the US were excluded for this study (N=2,691). All individuals who killed solely prior to 1970 were excluded (N= 2,370).  Also excluded were individuals who were missing information for key variables in this study such as date of first and last kill. The final sample (N=2,189) consisted of 2,061 males and 128 females.

The SPSS software version 23 (IBM Corp., 2013) was used to conduct chi-square tests on the included variables in this study. The relationship between eight of the variables (race of offender, race of victim, gender of offender, gender of victim, victim type, method of killing, suspected number of victims, years between first and last kill, region killed in, and the ninth variable (decade killed in) were individually tested. All chi-square results are significant at p <0.05. The variables were also each placed on a multiple line graph.

There were eight variables examined from the Consolidated Serial Homicide Offender Database: race of offender, race of victim, gender of offender, gender of victim, victim type, method of kill, suspected number of victims, and years between first and last kill. Two additional variables were created from the provided data information: region killed in and decade killed in. The following variables were recoded into groups for the purposes of the current research: race of offender, race of victim, method of kill, suspected number of victims, years between first and last kill, region killed in, and total serial killers per decade.

The initial categories for race (offender and victim) were white, black, Hispanic, Asian, Native American, and Aboriginal. These were recoded into white, black, Hispanic, and other due to the limited number of Asian, Native American, and Aboriginal killers/victims. The original methods of killing were bludgeon, gun, poison, stabbing, strangulation, pills, bomb, suffocation, gassed, drown, fire, starve, shaken, axed, hanging, order killing, staged accident, run over, pushed off cliff, abandoned, alcohol, drug overdose, electrocution, broken neck, withdrew treatment, and buried alive. These methods were recoded to include bludgeon, gun, poison, stab, strangle, suffocate, and other. If offenders used multiple methods, each method was counted once in its respective category. Suspected number of victims were recoded into groups of 0-4, 5-9, 10-14, and 15+. The same was done for years between first and last kill, resulting in the groups 0-5, 6-10, 11-15, 16-20, and 21+. Region killed in was determined by grouping states into four regions of West, Midwest, East, and South. A mixed region group was also included for killers who spanned 2+ regions. See Appendix for which states fell into each category. For decade killed in, a midpoint of each killer’s series was determined and used to place them as killing in the seventies, eighties, nineties, or between 2000 and 2009.

As seen in Figure 1, the number of serial homicide cases peaked in the 1980’s at 704, a number previously seen at 410 a decade earlier. As of 1990 this number dropped to 663, and continued dropping into 2000-2009. Overall, since its peak in the 1980’s the data shows a continuous decline in serial homicides. In the data, 18.7% of cases occurred in the 1970’s, 32.3% in the 1980’s, 30.3% in the 1990’s, and 18.8% in 2000-2009.

Offender Race: Of the serial killers in the data set, 49.9% were white, 41.4% were black, 6.45 were Hispanic, 1.6% were identified as other, and 0.6% were missing racial data. Figure 2 shows that serial homicides committed by offenders of each race have been in a decline for at least the past 20 years. The number of serial homicides by white offenders peaked in the 1980’s, while those of black, Hispanic, and “other” offenders peaked in the 1990’s and have also been in a decline through 2009. At a significance level of p= .000 and 9 df there is a significant relationship between race of offender and the number of serial homicide cases per decade (see Figure 3). There were 13 (0.6%) cases missing from this result. Despite the fact that white offenders held the highest percentage of serial homicides in the 1970’s and 1980’s (63.6%, 58.1%), between the 1970’s and 2000-2009 serial homicides by white offenders dropped by 29.9%. As white offender cases decreased, black and Hispanic offender percentages rose. Although the percentage of black serial homicides has continued to increase since the 1970’s, the number of cases have decreased, with 72 fewer cases in 2000-2009 than the peak in the 1990’s. The same is true for the number of Hispanic offender cases, going from 55 in the 1990’s to 36 in 2000-2009. The percentage of “other” offender cases remained relatively stable over time, but the number of cases all decreased from 13 in 1990’s to 5 in 2000-2009.

Victim Race: Of the victims in the data set, 42% were white, 15.4% were black, 2.2% were Hispanic, 18.7% were identified as other, and 21.6% were missing racial identification. Figure 4 shows serial homicides with white victims peaked in the late 1970’s and entered a steady decline. Serial homicides with victims identified as “other” peaked in the late 1980’s and then entered a sharp decline into 2000-2009. It appears that cases with black or Hispanic victims have yet to reach their peak, and as of the 2000-2009 data, were on an incline. At a significance rate of p=.000 with 9 df there is a significant relationship between the race of victims and the number of cases of serial homicide per decade (see Figure 5). There were 473 (21.6%) cases missing from this result. The percentage of white victims dropped 37.6% between the peak in the 1970’s and the 2000-2009 data. The percentages and numbers for black victims has increased between these decades by 29.7% while Hispanic victims increased by 3.2%. From its peak in the 1990’s (29.4%), the “other” category victims have decreased 6.7%.

Offender Gender: Male offenders make up 94.2% and female offenders make up 5.8% of the serial killer data used. Figure 6 demonstrates a peak in male offenders in the late 1980’s with a slight but steady decline until the 1990’s, followed by a sharp decline through 2000-2009. It also shows a sharp decline in female offenders into the late 1980’s after a peak in the late 1970’s, followed by a steadier decline through 2000-2009. Despite clear declines shown in both male and female offenders by Figure 6, there was no significant relationship found between gender of offender and the number of cases per decade.

Victim Gender: Of the victims in the data set, 25.3% were male and 32.9% were female, while 37.1% killed victims of both genders, and 4.6% were missing gender information. Figure 7 depicts the decline of male, female, and mixed gender victims. The number of offenses against male victims peaked in the late 1970’s and declined slightly but steadily into the late 1980’s, followed by a sharper decline into 2000-2009. Offenses against mixed gender victims followed a similar trajectory at a slightly lower percentage, while female victimization peaked in the late 1970’s followed by a sharp decline into 2000-2009.             At a significance level of p= .001 and 6 df there is a significant relationship between gender of victim and number of cases per decade (see Figure 8). There were 101 cases (4.6%) missing from this result.  Although the number of offenses against male, female, and mixed gender victims have experienced an overall decline, the percentage of male victims has increased by 12% since the 1970’s and the percentage of mixed gender victims has increased slightly since the 1980’s (1.2%). 

Years in Series: Most offenders in the data set (68.1%) had 0-5 years between their first and last kill. A much smaller number, 12.2%, had 6-10 years between, while 9% had 11-15. The smallest amount (4.9%) had 16-20 years between first and last kill. Those who had 21+ years between consisted of 5.9%. Figure 9 shows that the number of cases for all categories of years in a series have seen a decline. The sharpest decline is between those with a first and last kill spanning 16-20 years. This category peaked in the 1980’s and experienced a sharp decline in the 1990’s, followed by a more level decline into 2000-2009. The second sharpest decline is seen in the 21+ category, peaking in 1990’s and showing a sharp decline through 2000-2009. At a significance level of p= .017 with 12 df there is a significant relationship between the years between first and last kill and the number of cases per decade (see figure 10). As the 0-5 category increases from 1970’s to 2000-2009, the 6-10 and 11-15 categories decrease. Both the 16-20 and 21+ categories oscillate between increasing and decreasing, but all percentages stay below 10% throughout the 1970’s into 2000-2009.

Suspected Number of Victims: The majority of offenders in the database fit the victim count category 0-4 (75.1%). The second highest category, 6-10 victims, holds 12.2% of the data set. There are 3.9% of offenders in the data set with 10-14 victims, and 2.6% with 15+ victims. In Figure 11, the number of cases for all victim count categories show a decline into 2000-2009. The sharpest decline is in the 15+ category, which has been in decline since the 1970’s. The 5-9 victim count sees a sharp decline after its peak in the late 1970’s, while the 10-14 category sees a steady decline between the 1980’s and early 1990’s while continuing to decline into 2000-2009. Finally, the 0-4 category rose sharply between the 1970’s and 1980’s followed by a steady increase until the 1990’s and finally entered a decline into 2000-2009. At a significance level of p= .000 and 9 df there is a significant relationship between the suspected number of victims and the number of cases per decade (see Figure 12). The percentage of offenders with 0-4 victims increased between the 1970’s and 2000-2009 by 14.5%. All other categories decreased steadily between the 1970’s and 2000-2009.

Victim Type: In the data set, the highest percentage of victim type was acquaintance/strange at 30.7%. The second highest was mixed type (17.9%), and then home invasion (13.2%). All other victim type categories were each less than 10% of the data set. Figure 13 shows a decline in the number of cases for all victim types into 2000-2009. The sharpest decline is in hitchhiker victims, peaking in the 1970’s, steeply declining until the 1990’s, and continuing a steady decline into 2000-2009. A sharp decline is seen the 1980’s for family victims. Other sharp declines are seen in the early 1990’s for street victims, employee/customer victims, and criminal victims. At a significant level of p=.000 and 27 df there is a significant relationship between victim type and the number of cases per decade (see Figure 14). There were 133 (6.1%) cases missing from this result. See Figure 14 for results.

Kill Method: The data set has using a gun as the highest percentage kill method (54%), followed by stabbing (28%) and strangling (27.5%). Of the examined offenders, 17.9% bludgeoned their victims, 5.7% used “other” methods, 3.7% suffocated their victims, and 2.3% used unknown methods to kill. Finally, 2.1% poisoned their victims. Note that if a killer used more than one method, each method was counted individually in each category. Figure 15 depicts a decrease in the number of cases for all kill methods into 2000-2009. Each method shows a sharp decline in varying decades, with stabbing, and other peaking in the late 1970’s followed by a sharp decline. Bludgeoning, strangling, suffocating, and using a gun peak in the early 1990’s and decline into 2000-2009. At a significance level of p=.000 and 15 df there is a significant relationship between kill method and the number of cases per decade (see Figure 16). See Figure 16 for results.

Region Killed In: In the data set, 21.5% of the cases occurred in the Western region of the US. The Midwest had 16.5% of the cases and 14.3% of the cases were in the East. The South had 36% of cases while 11.6% were mixed or had cases across multiple regions. Figure 17 demonstrates a decline in the number of cases in all regions into 2000-2009. Cases in the West, Midwest, and mixed regions peaked in the late 1970’s while the Eastern and Southern regions peaked in the early 1990’s. The sharpest decline occurred in the mixed region category. At a significance level of p=.000 with 12 df there is a significant relationship between the region offenders killed in and the number of cases per decade (see Figure 18). The biggest decreases are seen between the 1990’s and 2000-2009. The Western region saw a 11.1% decline, the Midwest saw a 7.2% decline, the East a 13.1% decline, the South a 11.4% decline, and a 16.6% decline in mixed region cases.

Searching for Serial Homicide Victims Among The Hall of Justice Records

The Hall of Justice is a robust, searchable website that inventories criminal justice datasets containing semi-longitudinal records of 3,970 unresolved homicides across many US jurisdictions. Data was submitted by twenty-seven LEOs and classified into seven categories:  municipal (sixteen), county (two), metropolitan (two), state bureau of investigation (two), office of the prosecuting attorney (one), department of public safety (two), and sheriff’s office (two) and located in the following states and districts: Colorado, the District of Columbia, Florida, Georgia, Hawaii, Illinois, Indiana, Maryland, Massachusetts, Mississippi, Nevada, North Carolina, Oklahoma, Tennessee, Texas, Utah, Virginia, and Wisconsin. The population of these communities range from 51,000 to 5.3 million residents. Homicide watch programs (HWP) operating out of California contributed an additional 15,187 cases to this review. The number of unresolved homicides included in this review totaled 19,157 (see supplemental materials). To ensure the status of the record was updated and current, unresolved homicide records must have been sanctioned or maintained by a LEO or validated journalistic source. Unresolved homicide records contained on the LEO websites spanned from a low of three to a high of 1,347. The Colorado and Georgia Bureaus of Investigation and Texas Department of Public Safety contained records also maintained by local LEOs resulting in the removal of overlapping records from these jurisdictions. The earliest unresolved homicide originated in 1950 with recent records generated in 2016. LEOs maintained data for an average of 28 years and HWPs for 16 years. To create a cohort most closely resembling that perceived by those theorizing about an increase in serial homicide, this review focused on the number of female victims whose wrongful death resulted from strangulation, suffocation or asphyxia. Morton, Tillman and Gaines (2014) discovered that manual and ligature strangulation, suffocation and asphyxia were the primary cause of death in almost half of their sample (42.5%). There were no prerequisites for sexual violence to accompany the commission of the homicides in this review as sexually motivated murders were conflated with serial homicide, an artifact of a historical crime trend that coincided with the rise in academic scholarship into serial murder (Reid, 2017a). All homicides resultant from firearm usage were excluded from the review as gangland and professional hit killings would overtake the research. Of the 19,157 unresolved homicides, 229 (1.2%) were committed against females and caused by strangulation, suffocation or asphyxia. The low occurrence complements Schlesinger’s (2001) argument that serial homicide is not increasing given the victimization of women, the most common victim type among serial murderers, actually decreased from 33 percent in 1960 to 24 percent in 1998.

Comparative Analysis of Known Resolved and Known Unresolved Serial Homicide Series

Involving only known or apprehended serial offenders in a review of prevalence invites selection bias (Harbort & Mokros, 2001; Kiger, 1990) to overtake efforts to understand serial murder cases (Mott, 1999). Counts of separate and unique known unresolved serial homicide series were collected from various sources – media reports, textbooks (Mendoza, 2002; Newton, 2006), independent datasets (Mott, 1999; Quinet, 2011) and cases files submitted to the authors by members of Northeastern University’s Atypical Homicide Research Group[4]. A total of 107 known unresolved serial homicide series spanning four and a half decades resulted in an estimated 850 victims were assembled (see supplemental materials). Series conclusion dates were used as the endpoints and overlaid with counts of known resolved series from the CSHOD. The 1970s was selected as an appropriate starting point due to improvements in record keeping and tracking. The results (displayed in Figure 19) demonstrate that the decline has co-occurred in both the known unresolved and known resolved serial homicide series. The trajectory of both the highest and lowest points among the known unresolved and the known resolved series follow alongside each other in parallel throughout the decades. Because new discoveries of unresolved series are at the lowest point in recorded history - with the number of known unresolved serial homicide series having been halved with each passing decade after the peak of the phenomenon in the 1980s - fears that hundreds of unknown serial killers are roaming the country trolling for victims should be quelled. The offenders responsible for half of the unresolved series in this query are, in all probability, either dead or retired given that most serial murderers begin their careers at 32 years of age and are active for an average span of three years (Aamodt & Yaksic, 2015). Members of the public should rest assured that further victimization resultant from the unknown offenders included in this investigation is unlikely due to a general unwillingness to continue with their campaigns, self-imposed restrictions or those of a biological nature, such as age.

Qualitative Analysis of Thoughts on Unresolved Murders in the Context of Serial Homicide

To qualitatively understand current attitudes on how missing and unidentified persons, unsolved murders, no-body homicides, equivocal and mislabeled deaths, the “missing missing” and the unclaimed dead relates to serial homicide and present balanced concurring and alternate perspectives, thirty-two thought leaders and subject matter experts were consulted (Table 1). The roles of respondents varied widely across LEO representatives (7), society, foundation or center representatives (5), professors (15), subject matter experts (6), and journalists (2).

LEO representatives disagreed with the premise that serial homicide is declining as the number of killers uncovered by government efforts is expansive, especially when coupled with the thousands more case linkages that would be possible if ViCAP was used to its full potential. Most respondents felt that the lack of data on serial murderers could be explained by the limited resources and administrative issues beleaguering LEOs and hampering efforts to apprehend evolving offenders that are more cautious and learning from the mistakes of others”. One respondent noted that the numbers of annual new unsolved homicides, missing persons and unidentified bodies are “startling” and that our record keeping systems are too inadequate to accurately monitor these categories to determine their standing at the end of each year in which they were reported. Professors on the whole were not convinced that serial homicide is increasing since our detection of serial murder has improved while the overall counts are diminishing. Respondents were adamant that “there is no persuasive argument to attribute any significant number of cold cases and missing people to serial killings” and no reason whatsoever to believe that any meaningful proportion of unsolved cases are the result of serial killers” describing efforts to attribute the recent homicide spike to serial killing as “ludicrous”. Another respondent pointed out that the world is safer now than at any other point in history but was careful to remind of our use of anecdotal clues which provided much of what we know now about violence. One respondent suggested that there is no “credible evidence that the number of missing persons that are actually homicides not yet known to police is very large.” Another called for “an empirically based assessment tool to minimize cognitive biases associated with simplified heuristics based on individual investigators' experience.” Representatives from societies, foundations and centers stated that official statistics regarding missing and unidentified persons, unsolved murders, no-body homicides, equivocal and mislabeled deaths and the unclaimed dead are unavailable and that estimates are relied upon to guide knowledge. One respondent stated that “there are huge gaps in data gathering which leads to guesstimating the real numbers” and that “wild guesses are dressed up to look meaningful.” Representatives from the National Missing and Unidentified Persons System (NamUs) indicated that it is “far harder today to create a John or Jane Doe” and introduced a measure of skepticism that “a majority of the 40,000 unidentified human remains can be chalked up to serial killers.” One respondent warned that serial murder will increase because “the entropy of any isolated system always increases as a function of time”. Both reporters, each supervising their paper’s homicide tracking database, were confident that serial murders are the minority exception rather than the norm among homicide cases, each noting that the hallmarks of serial homicide (strangulation, mutilation, dismemberment) are found just as often in interpersonal homicides. Subject matter experts believe that our lack of knowledge bolsters offenders and makes their careers longer. One respondent observed that researchers tend to “rig the numbers” associated with victim thresholds to evidence theories.

Those supporting the idea that serial homicide is in a state of decline tended to be from fields outside the serial homicide mainstream. Most of the respondents thought it unreasonable to classify any statistically meaningful proportion of missing persons cases as homicides, let alone victims of serial homicide. The contrast in opinions between LEOs and professors warrants further investigation as biased or uneducated viewpoints may result in repeating stereotypes and reliance on myths.

Suspected and Probable Explanations for the Observed Decline in Serial Homicide

The Killing Season promulgates the message that serial murders are an overlooked and preventable facet of society whose offenders capitalize on systematic ignorance and broken systems to elude authorities, be they communication barriers among LEOs, weak mental health structures, ineffectual legal proceedings and inadequate deterrents; concepts working in tandem to allow thousands of offenders free reign to kill unmonitored and with impunity. We must appreciate that serial killers are the result of combinations of highly unique factors (Homant & Kennedy, 2009) functioning in terms of widely shared cultural and psychological processes (Shanafelt & Pino, 2013) whose actions occur within a social context (Shanafelt & Pino, 2015). The influence of social factors on serial murderers is important when considering changes in the incidence rates of serial killing over time, such as a few decades (Homant & Kennedy, 2009). While The Killing Season showrunners correctly assessed the current state of academic inquiry as criminological literature has shifted attention to the mass homicide offender in recent years, we pay serial murderers an unhealthy amount of attention through newspaper headlines and entertainment media, disproportionate to their presence in society.

The unintentional byproduct of this attention pushes some that maintain homicidal ideation into behaviors not typically attributed to serial murder typologies such as a greater utilization of the underground sex trade and human trafficking networks, warehousing abductees (Conti, 2015), altering their modus operandi, retiring early or adopting tactics associated with the spree murderer (Aamodt & Yaksic, 2015). Quinet (2011) credits progress made since the 1970s regarding the reduction of the serial murderer’s active killing periods and the average length of time they remain active. The landscape of multiple-murder has undoubtedly been altered by advances in technology as the Internet provides would-be offenders an open forum to explore the activities associated with leisure (Williams, 2016) – collecting pornography, taking photographs, journaling, paraphilic behavior – and the opportunity to placate themselves without exploiting unwilling participants while decreasing the need to eliminate complaining witnesses with such regularity - much the same as virtual reality gaming supplies a vicarious outlet for violence, absent of the physical victims. Certain ruses, such as posing as a photographer, are no longer plausible as the veracity of others can be easily verified. Jurisdictional conflicts between LEOs have subsided in favor of increased collaboration with surrounding departments. Many of the longstanding myths have been broken, specifically regarding the “white, male, loner” stereotype (Bartels, 2017; Branson, 2013; Hickey, 2014; Kuhns & Coston, 2005; Walters, Drislane, Patrick, & Hickey, 2015; Yaksic, 2006) an invaluable service since more serial crimes remain unsolved when investigators adhere too firmly to stereotypes (Mott, 1999). The public is consulted for assistance (Backus, 2015a) more frequently as advances in technology have made it easier for LEOs to ensure that abduction attempts (Larimer, 2016) are far less successful than in the past and to consider that a serial offender may be operating in their area (Kaste, 2015). The advent of cell phones, always connected social media accounts, assault prevention software (Glaser, 2016), facial recognition (Waddell, 2016), crime awareness mobile applications (Summers & Johnson, 2016) and the dawn of the surveillance age place offenders at exceptional risk of being detected far earlier in their careers (Sane, Mugadlimath, Farooqui, Janagond, & Mishra, 2017). Society has reversed a trend of ignorance of the serial murderers’ means and motives that had allowed them freedoms they can no longer enjoy.

A plethora of would-be serial murderers have been captured in recent years as LEOs clear rape kit backlogs (Mai, 2017; Waltke & Ames, 2017) and use familial DNA to reveal offenders (Pelisek, 2017) or take advantage of younger offender’s inexperience and incompetence before they amass greater body counts. Terms such as “budding”, “potential”, “becoming”, “obsessed”, “in-training” and “possible” are often used in conjunction with the phrase “serial murderer” to describe offenders that either admit to maintaining serial “tendencies” or outwardly display a desire to murder additional people upon capture for their first attempted or completed offense - Michael Hernandez, aged 14 (Associated Press, 2008); Steven Miles, aged 16 (Campbell, 2014); Andrew Conley, aged 17 (Shahid, 2010); Pearl Moen, aged 17 (Andrews, 2017); Leo Boatman, aged 19 (Ives, 2006); Daniel Stani-Reginald, aged 19 (Callaghan, 2014); Matthew G. Williams, aged 19 (Lynn, 2011); Fabian Rubio, aged 20 (Spencer, 2016); Andrew Busskohl, aged 21 (Anderson, 2011); Quintin O’Dell, aged 21 (Collison, 2012); Mark Howe, aged 21 (Gibson, 2014); Mario Swain, aged 22 (Associated Press, 2012); Denzell Thomas, aged 23 (Zavadski, 2016); Amy Caroline Brown, aged 24 (Tribune Media Wire, 2017); Terique Hall, aged 24 (Schultz, 2016); Steven Walter Robinson, aged 25 (Foxhall, 2015); Daniel Spain, aged 25 (Culver, N. (2015); Alex Bridges Deaton, aged 28 (Apel, 2017); Tony O’Toole, aged 29 (Alwakeel, 2013); Luke Magnotta, aged 30 (Ross, 2012), Travis Forbes, aged 31 (Steffen, 2016); Mark Twitchell, aged 31 (Bennett, 2011).

Other young serial murderers are not expressly branded even when satisfying the standard classification criteria. These killers would go unnoticed by search algorithms if not for off-handed comments by LEOs, victim’s family members or neighborhood watchdogs. Due to a tenuous grasp of the current definition, some LEOs hesitate to label young killers, like Christopher Allen Scheibe, aged 28 (Weathers, 2016), or Derek Richardson, aged 27 (Rizzo & Vendel, 2013), with the serial killer term. One LEO, cognizant of the future dangerousness of Brennon Lovett, aged 32, labeled him a serial killer that was “successful only once” referencing his numerous attempts to kill (Goforth, 2016). There are individuals, like Khalil Wheeler-Weaver, aged 20, that are reluctantly referred to as serial murderers due to the nature of their acquaintance relationship with the victims (Crimesider Staff, 2016a). Speculation surrounds other suspects like Christopher Revill, age 32 (Crimesider Staff, 2016b), and Kylr Yust, aged 27 (Killoran, 2017), as spurious links between homicides are made by the victim’s family members. The majority of these aforementioned serial murderers had their careers ended by LEO intervention at the age when those with higher body counts were just beginning their own campaigns. If LEOs continually improve upon their methods and techniques, the undiscovered population of young offenders may maintain homicidal ideation involving serial homicide without opportunities for achieving their goals.

In contrast, speculation falls upon older offenders from the outset, persisting even after their false positive status is revealed. The nature of the victim’s death, performance of postmortem activities or existence of items in the offender’s possession is coupled with the alleged offender’s age leading to the persistence of accusations even after such claims proved untrue (John Charlton, aged 37 (Truesdell, 2016); Gregory Hale, aged 37 (Jauregui, 2014); Neal Falls, aged 46 (Bailey, 2015); James Worley, aged 57 (Lindstrom, 2016)). Some news outlets take great pains to explain why certain offenders, like Jeffrey Willis, aged 46 (Gaertner, 2016), should earn the title and some LEOs conduct operations with such definitiveness that suspects like Shawn Grate, aged 40, are described as “obviously” being a serial killer (Barbash, 2016). These biases place an undue focus on the assumed experienced older offenders while the impending generation is ignored, those inherently different and approach the world of serial murder in new, unique ways.

We now know enough about the nature of serial offending to preemptively assist would-be offenders in warding off potential symptoms (Andrew Reisner, personal communication, 6 May 2016) or directly address the malingering of individuals yearning to emulate these killers (Fischer, Beckson, & Dietz, 2016). Efforts to educate the public about the backgrounds of these offenders led to increased awareness of the hallmarks (Wall & Johnson, 2015) of odd behaviors (Gelinas & Hadjistavropoulos, 2015; Woollaston, 2015), stalking offenses (Lloyd-Goldstein, 2000), paraphilias (Yakeley & Wood, 2014) and violent tendencies toward animals (Broussard, 2016; Levin & Arluke, 2016; Patterson-Kane, 2015) or others in youth (Hartley-Parkinson, 2015). Keen to head off any possibility of raising a serial murderer, parents took note of these oft cited warning signs and instituted helicopter parenting techniques, coddling youngsters and providing positive feedback regardless of results (Hosie, 2017). The positive effects behind corporal punishment have been debunked as the technique has fallen from grace and even been criminalized (Resnick, 2016), sparing many children potentially abusive childhoods. Some parents that would otherwise be deemed unfit may have elected to ward off unwanted pregnancies preventing some would-be offenders from developing the requisite homicidal ideation. Efforts to discern the potential future criminality of individuals has begun as childhood forecasting gains momentum (Caspi, Houts, Belsky, Harrington, Hogan, Ramrakha, Poulton, Moffitt, 2016) while parents are reluctant to allow children to play freely without supervision (Aamodt & Surrette, 2013). The disappearance of the 1960s “if-it-feels-good-do-it” ethos led to a greater distrust of strangers and the abolishment of hitchhiking which has diminished potential victim pools. Harsher punishments and more restrictive use of parole ensures that would-be serial murderers are incarcerated for longer (Aamodt & Yaksic, 2015). Although it could be argued that multiple murder is still a topic of interest around the world (Donley & Gualtieri, 2017), serial murder is not viewed as the shortcut to celebrity it once was since news coverage of these events has lessened over the years. The open yet disposable nature of the world no longer supports serial murderers and their sense of sentiment or collection of items, namely photographs, necessary to fuel their rumination sessions and relive their crimes and mentally prepare for new ones without intrusion.

Future generations may witness an even greater decrease in victimization. As congregations continue to shrink and potential victims turn attention to alternatives that remove human contact from their day-to-day lives, serial homicide offenders will be unable to adapt to a future without ready access to people as potential victims migrate to services that will keep them indoors (Vincent, 2017). Two occupations that serial murderers gravitate towards - long haul trucking and the medical industry - are due to place workers under tighter scrutiny (Bostock, 2017) or replace them altogether (Davies, 2015). Countrywide rights movements are part of a coordinated effort to strip a generation of undrafted young men of their toxic masculinity and instill in them a respect for woman. The rise in the self-harm epidemic (Ingraham, 2016), specifically opioid use, may be removing future threats from society preemptively.


Despite media portrayal and citizen perceptions of an epidemic of serial homicides, a debate exists among researchers about whether serial homicide may actually be in a decline. The goal of this study was to use the Consolidated Serial Homicide Offender Database to establish that there is a decline in known resolved serial killings and to examine a number of variables provided in the database. The study determined that almost half the percentage of cases existed in 2000-2009 than at the peak of serial homicide in the 1980’s. All eight variables demonstrated a significant relationship with a decrease in the number of cases per decade, showing that this decline is consistent across demographics, victim counts, time between first and last kill, and regions killed. In recent decades, there have been fewer serial killers with much smaller victim counts and shorter spans between their first and last kills. The cause of the decline in serial homicide may be attributed to the factors responsible for the overall drop in violent crime since the 1990’s as well as the developments in law enforcement techniques, developments in technology, and increased personal safety measures over time.

There were three findings contrary to the hypothesis: the percentage offenses committed by black offenders increased since 1970’s continuously, the percentage of black and Hispanic victims increased consistently since the 1970’s, and the gender of the offender was not significant. The increase in the percentage of black offenders may be a result of a change in the assumptions and stereotypes of the serial killer, which has always been of a white male. The change in this idea may have resulted in an increased pursuance of black suspects and therefore a higher percentage of apprehensions. Since murder is often intra-racial, an increase in the percentage of black offenders in theory would lead to an increase in the percentage of black victims. The lack of a significant relationship between the gender of offender and the number of cases is most likely due to the overwhelming percentage of male offenders in the data set.

There are limitations in this study that may impact its results and/or conclusions. First, the Consolidated Serial Homicide Offender Database was built by amassing records mainly from journalistic sources, a problematic approach laden with drawbacks (Kiger, 1990). Morton, Tillman and Gaines (2014) overcame this obstacle by selecting only cases for analysis that were referred to the National Center for the Analysis of Violent Crime, a luxury not afforded academic researchers which results in missing information on a number of variables. Even though those variables used in this study were only missing small percentages of data, any missing information is a limitation. The dataset variable categories are also constructions of the present authors and therefore might not be universal to all researchers or cases. Another limitation of this study is the use of chi-square analyses. Due to the statistical information provided by such a test, the direction and degree of the significant relationships cannot be determined. Therefore, assumptions are made in the conclusions about the significance. In an attempt to overcome the dataset limitations, a large sample size was used and the majority of offenders missing key data were excluded from the analyses. Despite the limitations of the chi-square tests, the belief is that the multiple line graphs corroborate the direction of the statistical relationship that is assumed in the conclusions.

Findings from the review of the Hall of Justice records are not generalizable as McNamara and Morton (2004) warn that unique geographic, economic demographic and cultural issues limit the representativeness of a sample when attempting to accurately project the national percentage of serial homicide offender victimization and that no state should be utilized as a template for projecting the total amount of serial murderers in the US. Many aspects of the review, such as potential victim-offender relationships and probable abduction scenarios, were open for interpretation because pertinent details, such as the presence of a suspect or person of interest, were unavailable. It was impossible to establish whether or not the unresolved strangulation murders were stranger homicides forcing the present authors, without such confirmation, to approximate that only a fraction of the unresolved homicides included in this cohort will contain killings that could conceivably be serial homicide victims. Additional resources were required when seeking supplemental narrative details as they were not consistently provided. One drawback of relying on LEO websites is that the full case list is not always made available (Friedenberger & Stevens, 2017) which, along with site updates once a case is resolved, affects the reproducibility of this aspect of the study. The exclusion of entire states was sometimes necessary due to missing, inconsistent or unclear information, typically related to the method of death. Records originating from the District of Columbia evidence how insufficient narrative details contributed to the exclusion of thousands of firearm homicides. The review performed by the present authors of these unresolved homicides could be classified as too subjective to be meaningful as well as underpowered since the review covered only a fraction of the estimated 230,355 unresolved homicides in the US identified by Stein (2017). Although the review was influenced by the combination of two popular concepts in serial homicide research – females that were strangled– these parameters may have unduly narrowed the scope, rendering it irrelevant due to the increased commonality of firearm deaths. 

Many of the problems present in this study are endemic to serial homicide research. The intervention of LEOs in the formative years of a serial murderer’s career prevent researchers from conducting longitudinal research on individuals like Christopher Duntsch (Guillen, 2017) or Gannon LeBlanc, aged 23 (Bienick, 2016), foiling attempts to determine which traits would have coalesced during the offender’s transformative process. Researcher fatigue (Bialik, 2016) may have contributed to erroneous results as strain induced by reading reports containing information about a death can be unsettling. Obviously resolved homicides provide researchers the opportunity to analyze known events and personality defects attributed to readily available and tangible offenders but it cannot be understated how studying unresolved homicides in an in-depth manner is hampered by uncooperative arbiters, fears of condemnation from peers and constant reminders that what is not known cannot be known each forcing a reliance on heuristic techniques to fill the void. It was not possible to assemble an exhaustive list of known unresolved serial homicide series due to incomplete records. LePard et al. (2015) identify the challenges in serial murder investigations related to missing persons namely that some are never reported to the police, those that are can sometimes be overlooked as transient and the proportion that are serial murder victims are revictimized by compromised or impeded investigations due to the absence of forensic evidence. Stein (2017) conducted a survey of 10,500 law enforcement agencies and found that approximately 56% of the agencies said they have cold cases, yet only 19% of those have a dedicated cold case team consisting primarily of one to two detectives. Giannangelo (2012) points out that facts and analysis of both concluded cases and theoretical concepts accepted for years may or may not be accurate, and may continue to evolve.


Rather than addressing the etiology of these offenders and the criminogenic factors that contribute to and influence their choices, much of the academic literature on serial homicide focuses on the creation of better detection methods. Some measure of consternation is involved in unraveling the reasons behind the decline because it forces researchers to acknowledge that serial murderers are people impacted by societal shifts and cultural norms as opposed to monsters mindlessly trolling and seething. Providing the decline with ample attention and consideration requires researchers to break away from their areas of expertise and adopt a wider variety of emphases (Shanafelt & Pino, 2013). DeLisi (2015) holds serious researchers accountable for limiting the scientific understanding of serial murder by shunning it as an aberration, relegating its study to other communities such as true crime authors and expert practitioners which leads to a lack of innovation in scholarly thought. The traditional role of a subject matter expert has consisted of appearing in news items while fielding questions related to the offender’s accomplishments corresponding to body counts or gruesome methods of deaths. Resultantly, researchers rarely attempt to effect change in this arena and instead report and interpret the facts, as they are understood at the time. Omitted from the equation is any description or explanation of fluctuations in the data mainly because researchers are frustrated that much transpires without their involvement. What is disconcerting to researchers is that the decline in serial homicide has happened largely outside of systematic efforts on the part of academics to orchestrate it, contributing to a general sense of disbelief in the phenomenon.

Future research should perhaps be less concerned about whether or not the decrease has occurred but rather why the spike happened in the 1980s (Dimond, 2014). The complexity of multiple interacting variables is often too complicated for us to completely understand, especially given the small choices made in everyday life that send us down paths neither anticipated nor entirely predictable (Shanafelt & Pino, 2013).The decline partially evidences that choices among the serial homicide offender population are possible and that small changes in their background experiences have tremendous effects. Researchers have struggled with the suggestion that not all serial murderers are predetermined to become killers or that they are not compelled to complete their actions. Proponents of the idea that serial homicide is increasing at exponential levels may fall victim to creating and exaggerating a social problem (Kiger, 1990) and run the risk of being exposed as yearning for a return to the phenomenon’s heyday, one rife with the promise of profitability. Because DeLisi, Tahja, Drury, Caropreso, Elbert, & Heinrichs (2016) draw a distinction between most homicides being reactive, expressive and impulsive actions and those entailing homicidal ideation or planning and contemplation to complete instrumental homicides, future research should explore whether or not modern day offenders engage in homicidal ideation and simply fail to follow through with their schemes or if thinking about committing murder has dissipated along with falling homicide rates. A true estimate of serial homicide offending will forever be incomplete unless it incorporates those that intended to murder serially but whose efforts were stalled by arrest, imprisonment or death.

The current research depicts a decline in serial homicide, which, would benefit from improvements and expansion in future research. It is suggested that an effort be made to further complete the Consolidated Serial Homicide Offender Database. Regardless of this step, future research should perform more extensive statistical tests on the data in order to replicate these findings and determine the direction and degree of any significant relationships. In order to move on to any inquiries into why there is a decline in serial homicide, the intricacies of this decline must be further examined. Subsequent research would benefit from sustained offender tracking to determine whether the decline has continued through into the future. Although the results of the current study may surprise members of the media and citizens of the US with a cultural fascination with violence and fear, there is a decline in serial homicide.

This research does not intend to minimize the suffering of victims or their families. Serial murderers remain threats to the public (Crimaldi, 2017) and no one should be dissuaded from seeking justice for victims by following evidentiary trails, even if arrived at as byproducts of hutches or exploitation of the Doctrine of Chances. Although the criminal justice system is undergoing rapid changes with instances of police abuse, brutality and unjustified shootings (Serwer, 2017), continued use of questionable forensic techniques (Green, 2017), discovery of rape kit backlogs (Reilly, 2015) or prosecution of innocent men and women (Segura, 2017), serial homicide offenders are not waiting to reemerge and capitalize on a structure in disarray. Only time will tell which way trends will shift but the present authors hope that the serial homicide landscape as it was once known in prior decades has been permanently transformed for good.

[1] similar demographics (single, white, female), proximity of remains (small geographic zones), identical methods of death (typically “hands on” means like strangulation or asphyxiation), and the presence of non-standard pre/post mortem activities (i.e. abduction, sexual assault, mutilation or dismemberment) also known as the “Gone Girl Profile”
[2] For the purposes of this paper, the decline in serial homicide is conceptualized as merely a decrease in year over year discoveries of new serial homicide series via apprehensions or clearances based on validated offender confessions or forensic linkages after their deaths. Homicidal ideation and the desire to become a serial killer may, in fact, be on the rise given admissions of young killers. The decline will never result in the complete and total stoppage of serial killings and that happening is not implied at any time in this paper.
[3] Serial murderers often alter their methods over time (Larson, 2017) or even when killings are minutes apart (Collins, 2017)
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