Hickey agrees, adding that police antipathy for sex workers further frays the lines of communication. Because sex work is illegal (in most of the country), prostitutes are far less likely than the general population to report victimization of themselves and their colleagues to the police.
"Generally, police are not real fond of prostitutes, because there tends to be other kinds of crime going on when there's prostitution in the area," he says. "And so when someone goes missing, maybe one of their friends who is also a prostitute might go and report it… but usually, from the stories we hear, there are two or three prostitutes who disappear before they start to get a little nervous."
With the Long Island Serial Killer case, Kolker notes that when the last victim—Amber Lynn Costello—disappeared, neither Costello's sister nor her close friends reported her missing, because they too were involved in sex work and didn't wish to call police attention to themselves.
"It's a major factor, and something that everyone knows," says Kolker. "Including the killers."
In planning their murders, serial killers often try to bring their victims to a location beyond police detection or Good Samaritan intervention. Here, too, many prostitutes are vulnerable—especially those who don't work from a brothel, but instead go to secluded locations with their johns.
And because of the nature of their work, there's also an obvious sexual component to the relationship—often a key motivator for serial murderers, says Hickey. "About two-thirds of all male serial killers are sexually involved with their victims in some way," Hickey says. Prostitutes, he adds, are "low-hanging fruit."
To target people who aren't sex workers, serial killers often have to scheme: They might feign injury to garner sympathy, as Ted Bundy did, or spend weeks stalking their victim to detect vulnerabilities in habits. But when killers target prostitutes, it can be as simple as negotiating a fee from across a car window.
"It just takes a lot more planning to go after someone who is more educated, more socially savvy," Hickey says. "A prostitute is streetwise, but only to a certain extent."
Prostitutes are also regularly dehumanized—in the eyes of the law, in the eyes of the public and in the eyes of the killers themselves.
At his sentencing hearing, Gary Ridgway, the so-called Green River Killer who was convicted of more than 48 murders, summed this up when he said, "I picked prostitutes as my victims because I hate most prostitutes… I also picked prostitutes because they were easy to pick up without being noticed. I knew that they would not be reported missing. I picked prostitutes because I thought I could kill as many of them as I wanted without getting caught."
