Serial Killers: The Criminal Investigation Process

John Wayne Gacy & Gary Leon Ridgway

Cases in Point: John Wayne Gacy & Gary Leon Ridgway

A great deal of confusion and myth surrounds serial killers and the investigative processes used by law enforcement. Much of this myth and confusion results and promulgates due to media coverage. Further confounding this problem, an extreme lack of professional expertise in serial murder exists due to rareness of serial killers, making difficult for expertise to be obtained by any professional in the psychiatric or criminal justice fields. For these reasons, the FBI’s Behavioral Analysis Unit (BAU) identified specific investigative best practices for successful serial killer investigation. Examining individual serial killers clarifies utility of the BAU's investigative techniques.

John Wayne Gacy

Serial killer, John Wayne Gacy serves as a model for understanding the application of the BAU’s investigative practices. One of the worst difficulties when investigating serial killers stems from law enforcement's susceptibility to the same myths, misconceptions, and biases that haunt the general public. The BAU describes this problem:

Law enforcement professionals are subject to the same misinformation from a different source: the use of anecdotal information. Professionals involved in serial murder cases, such as investigators, prosecutors, and pathologists may have limited exposure to serial murder. Their experience may be based upon a single murder series, and the factors, in that case, are extrapolated to other serial murders. As a result, certain stereotypes and misconceptions take root regarding the nature of serial murder and the characteristics of serial killers (US Department of Justice).

The misinformation factor often has a blinding effect on law enforcement, especially in the identification process, which the BAU identifies as the most important investigative practice in serial investigation. One readily sees the importance of this point in the investigative process during the John Wayne Gacy case. Between 1972 and 1978, Gacy raped, tortured, and killed a known thirty-three young men (Federal Bureau of Investigation). Gacy killed so many individuals primarily because he went unidentified as a serial killer until 1978. In 1976 a family member of one of the victims urged police to investigate Gacy and twice after that incident Gacy would be accused by two individuals of rape, but police failed to act (Federal Bureau of Investigation). Compounding this failure is the fact that Gacy already served time in prison for sodomizing a young man.

Gacy continued killing due to the fact that, in many instances, police lacked the investigative skill or means to identify the serial killer. Serial killers are rare and most law enforcement does not have the expertise to identify or link situations in a way that reveals the possibility of serial killing taking place. Circumstance adds to this problem as the police involved with Gacy also found the claims of the persons who accused Gacy to lack credibility. At the time, communication proved problematic also because incidents could not be connected by investigating officers since police who investigated the second complaint had no idea of a prior complaint. The BAU discusses this problem as a “lack of communication between law enforcement agencies and differing records management systems impede the linkage of cases to a common offender” (US Department of Justice). Communication has historically been an issue in serial killing investigation because serial killers don't respect jurisdictions and often travel across state lines murdering, making linking cases difficult even today.

Despite inability to recognize Gacy as a serial killer, once known, extremely proficient leadership of the investigation began quickly piecing together the Gacy murders from individual family and victim reports. The lead investigators were both competent homicide detectives and this was exactly what was needed according to the BAU.

In serial murder cases, the actual investigation should be directed by competent, homicide investigators, who have the experience to direct and focus the investigative process. Law enforcement administrators should not run the investigation but rather ensure that the investigators have the resources to do their job. Supervisors should also act as buffers between investigators and the other levels of command (US Department of Justice ).

Once investigators began focusing on Gacy, they were allowed to handle the case with very little pressure from superiors and from the public. Gacy was arrested after several months of investigation and a confession was obtained after his arrest. The investigation of Gacy included the questioning of victims and associates of Gacy which allowed for investigators to obtain search warrants in order to search for bodies in the Gacy residents. In many ways, the Gacy investigation was a model serial killer investigation because there were no strong or public personalities involved and there was little micromanagement of the investigation process (Federal Bureau of Investigation).

Another area of competency seen in the Gacy case elucidates from the use of analytical tools. The investigators were skilled in many areas such as “crime scene analysis, offender profiles, case linkage analysis, interview strategies, and prosecution strategy” (US Department of Justice ). For example, the lead investigators entered the Gacy home at his invitation and while one investigator kept Gacy busy the other was able to go into the bathroom where he smelled decomposition coming from the air vents. Prior visits from police were unable to detect this smell (Federal Bureau of Investigation). Investigators were also able to create accurate timelines of victims and link these cases in a meaningful way for the prosecution to use at trial. Investigators were able to obtain future search warrants due to their ability to accurately investigate the scene. The competence of investigators and their use of analytic tools were important factors for bringing Gacy to justice. This is especially true during this time period when DNA testing was not being used. The investigation depended strongly on the ability of investigators to link Gacy with victims and discover other forensic evidence such as victim belongings and match them to the victims using family and acquaintances.

The fact that investigators were well trained and had operational discretion over the Gacy case highlights the need for serial investigations processed within specific parameters and standards. The Gacy cases show how identification is perhaps the most important aspect of the serial killer investigation but the case also highlights how a case should be conducted once the serial killer is known.

One of the major issues which often occurs during serial killer investigations is what is known as the talking head phenomena. This is the issue of self-proclaimed experts who are given credibility by the media in serial killer cases. These so-called authorities often appear on television and in other media outlets and speculate concerning the motives and the causes of the serial killer as well as possible characteristics of the offender despite having no direct involvement with the case (US Department of Justice ). Unfortunately, the talking heads can often create barriers to the investigation because they perpetuate myths and misperceptions that impair nonexperts in law enforcement. Some of the myths perpetuated by these individuals and other media outlets include: 

Serial Killers: Data From FBI

Except for being white and having sex as a part of his modus operendi, Gacy did not exhibit any of the other myths perpetuated in media concerning serial killers. In fact, Gacy was described as being a likable and respected member of the community (Federal Bureau of Investigation). He was active in community affairs. Gacy also did not operate across state lines and stopped murdering for extended periods (Federal Bureau of Investigation). Certainly, Gacy did not desire to get caught, judging from the lengths he went to avoid capture.

The lack of media sensation at the beginning of the Gacy case may have been a significant factor in his investigation and arrest. When one looks at other cases such as the Green River Killer, who arguably was as normal in appearance as Gacy, was recognized by police in the early 1980s.

The Green River Killer, Gary Ridgeway, confessed to killing 48 women over a twenty-year time period in the Seattle, Washington area. He had been married three times and was still married at the time of his arrest. He was employed as a truck painter for thirty-two years. He attended church regularly, read the Bible at home and at work, and talked about religion with co-workers (US Department of Justice ).  

Gary Leon Ridgway

The Green River Killer was spotlighted in the news and a task force was formed in the early 80s but Gary Leon Ridgway would not be apprehended until 2001. The length of time involved in apprehending Ridgway was due to the fact that he did not fit the profile myths that are typically perpetrated by media and by so called experts (US Department of Justice ).

Reflecting the seriousness of this problem, the prior case of the Atlanta Murders from 1979 to 1981 did not sway the bias of police in the Green River Killer case. Wayne Williams, a black serial killer, for many months eluded investigators looking for a white male until one investigator realized the necessity of the killer to be black to enter all black areas and operate unnoticed. This factor impeded the investigation for a long time, but once investigators refocused themselves to a new subject, they began making headway in the investigation.

It is cases such as Gacy’s and other serial murders that reflect both beneficial and negative practices. The rareness of serial killing dictates the need for officers to have more training and more standardized practices for proficient identifying and processing of serial murders. While John Wayne Gacy reflects failure in law enforcement recognizing the serial murders, his case also provides a model for how the investigative process should be handled. In the future, law enforcement will continue to improve as units such as the BAU continue to collect data and provide more effective practices for serial killer investigations.


Federal Bureau of Investigation. John Wayne Gacy Part 01 of 01. 1979. Internet. 28 April 2014. .

US Department of Justice . Serial Murder Multi-Disciplinary Perspectives for Investigators. 2005. Internet. 28 April 2014.

Photo John Wayne Gacy & Gary Leon Ridgway

Article Updated: 10/23/2022


Triola Vincent. Mon, Feb 01, 2021. Serial Killers: The Criminal Investigation Process Retrieved from

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