Whether it's possible to predict who will commit murder is an ongoing debate among psychologists, criminologists and law enforcement professionals. Now, new research from Bryanna Fox, a University of South Florida assistant professor of criminology, is helping answer this question with a first-of-its-kind project.
The new study, published in the journal, Aggression and Violent Behavior, analyzes data from 19 studies which contained information from more than 2,600 homicide offenders. Researchers looked at offenders' psychopathy checklist score to determine any potential relationship between the checklist data and homicides.
The psychopathy checklist is a diagnostic tool used to rate a person's psychopathic tendencies on a scale from zero to 40 — the higher the number, the more psychopathic a person is deemed to be. The most common method for assessing psychopathy, the psychopathy checklist measures 20 traits, including pathological lying, lack of empathy, superficial charm and many more. In the U.S., if someone scores 30 or higher, he or she is considered a psychopath.
The new study revealed an average score of 21.2 among the studied cases. And when compared to the 5.2 average among American adults, it's clear the psychopathy checklist indicates a potential for violent criminal behavior.
"There's a very high correlation between psychopathy and homicide," said Fox in a news release. She co-authored the study with Matt DeLisi, a professor from Iowa State University. "In our study, we found a correlation value of .68. In social science, anything above a .4 or .5 is considered strong — so these findings are very interesting."
Fox says that while the idea of the "psycho killer" has been prevalent in popular culture for years, there had never been an academic examination of the concept until now. She says that even though the offenders' average checklist score falls below the psychopathy threshold, the data could still provide useful information when during assessment.
Researchers say, however, that it is important to remember that there are no "thought crimes" and an individual cannot be arrested or convicted based on the likelihood they may commit a crime. Instead, Fox says the data could be used in a parole setting to help determine a convicted criminal's probability of reoffending and if they should be released prior to completing their sentence.
"It's very difficult at this point to say if (checklist) scores could be used predictively," Fox said. "But what it does tell us is that people who are scoring over 20 are in 'very high-risk' territory."
— Times staff