A Homicide Archivist's Chilling Estimate On Serial Killers In The U.S.

Serial killings are fairly rare. The FBI estimates serial killers are responsible for less than 1% of the murders committed in any given year in the United States. But this statistic is not without controversy, and there are some who believe that the bureau is off the mark.

Thomas Hargrove, founder of the non-profit Murder Accountability Project, first started gathering data on unsolved murders in 2010. Since then, he's gathered more than 750,000 records on murders dating back to 1976, according to The New Yorker. It's the largest database of killings in the country, and he's using it to try to find similarities between crimes that could indicate the work of the same killer. Based on the database and his code, the former investigative journalist is pushing back against the bureau's estimate and thinks there are actually a lot more serial killers out there.

FBI data suggests the number of serial killers has fallen dramatically — by as much as 85 percent — over the past three decades, according to The Atlantic. Among the reasons thought to be responsible for the decline: longer prison terms, fewer killers being granted parole, and better forensics. Other factors thought to be responsible for the drop are the proliferation of security cameras, fewer people hitchhiking, the prevalence of cell phones, and parents who monitor their child's every move, according to Discover Magazine. 

While there may be fewer Jeffrey Dahmers, John Wayne Gacys, and Ted Bundys roaming the streets, the ones that are out there killing are less likely to be caught than in years past. The homicide clearance rate refers to how many cases have actually been solved. In 1965, the U.S. rate was a whopping 91 percent. But in 2017, the number had dropped to just 61.6 percent. That means 40 percent of the time, killers are getting away with it, according to The Atlantic.

Thomas Hargrove believes that at least 2% of unsolved murders can be attributed to serial killers (about 2,100 killers on the loose), according to The Atlantic. So why does the FBI thinks it's only half that number? Hargrove says he asked people at the bureau to check the records for the number of unsolved murders that were linked by DNA (via The New Yorker). The results showed that more than 2% of the murders were linked through DNA, indicating the same person was responsible. Hargrove says his 2% figure could be even higher because DNA isn't present in all the cases. Another expert on the subject, Michael Arntfield, who's a retired detective and has written a dozen books on serial killers, thinks the number at large is even higher — perhaps as high as 4,000 (via The Atlantic)

Hargrove says he hopes his algorithm will eventually help law enforcement connect cases and solve a crime, according to The New Yorker. And he's working on a new project — tracking arson cases, because he says the same people who light fire after fire have things in common with serial killers.