Stats Reveal How Many Serial Killers Went Uncaught During The 20th Century


Tom Hale

Senior Journalist

clockOct 4 2021, 14:27 UTC

The figures in this new paper are notably lower compared to those reached by previous. Image credit: Motortion Films/

Ted Bundy, Jeffrey Dahmer, Richard Ramaierz. Many of America’s most prolific serial killers have burned their name into popular culture. However, for all the murderers who saw justice for their crimes and gained infamy, how many have slipped under the radar and remained uncaught?

Using statistical analyses, two researchers have worked out how many serial killers in the US potentially went uncaught over the course of the 20th century. 


Mikhail Simkin and ‪Vwani Roychowdhury‬, two researchers from the Department of Electrical Engineering in the University of California, Los Angeles, deduced that the 20th century likely saw approximately seven serial killers that managed to avoid being caught by authorities. Although they note “our estimate is on a lower side” in their yet-to-be peer-reviewed pre-print paper, they also surmise: “The most prolific of them likely committed over sixty murders."

The figures in this new paper are notably lower than those reached by other statisticians and criminologists. A study in the journal Homicide Studies in 2007 estimated there were between 182 and 1,832 serial murder victims that go unreported each year in the US. The study author, criminologist Kenna Quinet, told Live Science that this could equate to about 115 US serial killers dating back to the 1970s who were never charged for their crimes. Meanwhile, the Murder Accountability Project argues that there are up to 2,000 serial killers currently at large. Certainly, many of these will be caught eventually, but some are likely to avoid capture. 

So how did this new paper reach their conservative finding? The pair had to take into consideration a number of variables. For starters, they analyzed the data of 1,172 US serial killers documented in the 20th century and not just the 1,012 for which we know the exact date of their murders. Considering that many serial killers have periods of years, if not decades, between each murder, they then worked out what proportion of killers simply died of natural causes or accidents before the law caught up with them. 


However, this is where things become complex. Not all serial killers are as “effective” (if we can call it that) as others. Some will get caught after the first murder, while others could theoretically evade the law after dozens of murders. To fill this gap of knowledge, the duo ran statistical simulations of 1 million hypothetical killers. Out of this 1 million, 659,684 got caught after the first murder, 539 died after the first murder, 337,729 killers committed two or more murders but were then caught, and 2,048 committed two or more murders and were not caught. 

Based on the number of documented US serial killers, these statistics suggest that around seven people committed at least two murders in the US during the 20th century but did not get caught. 

There are some significant limitations to this analysis, the researchers concede. They note their paper did not take into account would-be serial killers that abruptly ended their killing sprees due to being incapacitated by ill health, disability, or old age. For instance, the so-called “Golden State Killer” Joseph James DeAngelo was caught in 2018 at the age of 72, but his last known murder was committed in May 1986. 


Active life span would be a better measure than simply life span, they note. As such, the fraction of uncaught killers would be only bigger. 

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