With an arrest in the case of the dormant Golden State Killer, the New York Times looks at what makes serial killers tick and, contrary to what you might think, it's not usually an insatiable thirst for blood. As forensic psychologist J. Reid Meloy explains, "These are not acts that a person is compelled to do. They are intentional and predatory. There is choice, capacity and opportunity that is exercised." That helps explain why the Golden State Killer appears to have gone quiet after 12 murders and more than 50 rapes in California between 1976 and 1986. Similarly, BTK Killer Dennis Rader ended his string of 10 murders in 1991, 14 years before he was arrested. He later admitted "to engaging in autoerotic activities as a substitute for his killings," as noted in a 2008 FBI report.
Though motives are hard to nail down, changes in stress level, location, work, and family have also had an impact on serial killers, per the Times. Michael H. Stone, another forensic psychologist, notes Green River Killer Gary Ridgeway's murder spree spanned his first two marriages but quieted following a happier third one. There was a five-year break in crimes attributed to the Golden State Killer after a daughter was born to suspect Joseph James DeAngelo in 1981, per the Los Angeles Times. But Stone speculates age is a factor, too. In 1986, DeAngelo would've been 40. At that age, "testosterone levels are down" and one's "capacity to perform is weakened," Stone says. Rape-murderers "are really rare over age 50," adds a retired FBI criminal profiler. "We just don't see them." (Here's how DeAngelo was identified.)