Catching a Serial Killer

A serial killer keeps killing until one of four things happens: he is caught, he dies, he kills himself or he burns out. Obviously once law enforcement determines that a string of murders can be attributed to one person, the goal is to catch him as soon as possible. But how do they figure this out? And how are serial killers caught?

green river killer
King County Prosecutor's Office/Getty Images
Investigators search for the remains of a victim of
Gary Ridgway, the Green River Killer.

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­In the aftermath of any homicide, inv­estigating the crime scene and performing an autopsy are routine steps that law enforcement takes in an attempt to solve the crime. Once all of this information has been collected, it can be entered into a nationwide database run by the FBI, as part of ViCAP (Violent Criminal Apprehension Program). This program can help to determine patterns, or signatures, that link separate homicides.

According to FBI profiler John Douglas, a signature "is a ritual, something the subject does intentionally for emotional satisfaction -- something that isn't necessary to perpetuate the crime” [source: JohnDouglas.com]. Some serial killers pose their victims in a certain way or leave them in a certain place after killing them. Another signature might be a method of torture or mutilation. It's what the killer does to fulfill his fantasies, and it can tell investigators a lot about his personality.

Investigators also look at the MO, or modus operandi, of the crime. The MO reflects what the killer had to do to commit the crime. This includes everything from luring and restraining his victim to the way that he actually murders her. A serial killer's MO can change over time. Essentially, he learns from past mistakes and improves with time.

Violence in the Genes?
Most people have two sex chromosomes, either XX (women) or XY (men). But some people have an extra X chromosome, which gives them Klinefelter syndrome. People with this condition are usually male and have lower testosterone levels than XY males. Some researchers have suggested that XXY men are more aggressive and are more likely to be physically abusive. Arthur Shawcross was found to be an XXY male. Klinefelter syndrome occurs in between
1 in 500 and 1 in 1,000 births [source: Palomar College]. So while it may be a factor, it certainly cannot be the only factor in determining the makeup of a serial killer