The bill is coming due for serial killers of decades past — most recently in the form of a new murder charge against Clark County’s own suspected serial killer, Warren Forrest.

Forrest, 70, has been convicted of only one murder, but he is now accused in the 1974 slaying of 17-year-old Martha Morrison of Portland. Investigators say DNA evidence linked the former Battle Ground man to her death.

He is believed to be responsible for the abduction and slaying of six women and girls in Clark County in the 1970s, and he is a person of interest in another missing persons case.

Better understanding of serial murder, as well as advances in DNA testing and handling of forensic evidence, are helping to bring long unidentified or suspected serial killers to justice and closure to the victims’ loved ones.

The public’s fascination with serial killers continues to grow, even as the number of high-profile cases has declined since the 1970s and 1980s.

What is a serial killer?

Serial murder — the unlawful killing of two or more victims by the same offender in separate events — makes up less than 1 percent of all murders in any given year, according to the FBI.

Radford University’s Serial Killer Database, maintained in collaboration with Florida Gulf State University, has identified 3,596 serial killers in the United States since 1900.

Serial killers often have families, homes and jobs. They span all racial groups and can have multiple or evolving motivations for killing: sex, anger, thrill, financial gain and attention seeking. Most operate in defined comfort zones. They choose to kill, and some stop depending on their personal circumstances. Many have personality disorders. But above all else, serial killers think they can’t be caught. It’s a sense of empowerment that often leads to slip-ups and their eventual capture, according to a 2008 report from the National Center for the Analysis of Violent Crime.

Forrest, a Vancouver native and Vietnam Army veteran, had married his high school sweetheart; they had two daughters. He supported his household, working for the Clark County Parks Department. But he also abducted, raped and tortured a woman, and left her for dead in 1974. Except this woman survived, and her testimony helped convict him of the 1974 murder of Krista Kay Blake, 20.

“There are monsters in this world, but they don’t walk around with a red ‘Monster’ on their forehead,” said Norma Countryman, one of the two known victims who survived Forrest. “In his soul, he’s a monster.”

‘Cocktail of things’

Certain traits are common to serial killers, such as sensation seeking, a lack of remorse or guilt, impulsivity, the need for control and predatory behavior, according to the FBI’s 2008 report. Serial killers choose their victims based on availability, vulnerability and desirability.

“I think the impulses serial killers act upon are deeply ingrained — animal impulses for survival, flee or fight, the sexual impulse and feeding impulse. Now that we’re civilized, these are anti-society impulses,” says Peter Vronsky, Canadian historian and author. “I think we’re all born with those impulses, but we’re socialized out of them.”

Statistically, the average age serial murderers begin killing is about 28, according to Michael Aamodt, the professor emeritus who created Radford University’s Serial Killer Database. Vronsky said many report their first rape or homicidal fantasies between the ages of 5 and 14.

Forrest admitted that he started to have vague thoughts about the crimes he would eventually commit when he was 15 and wanted to feel more masculine, according to a 2013 progress report from his sex offender treatment program. Later, he found he became aroused by violence.

Among the shared experiences of many serial killers is neurological injury and childhood trauma or abuse — an unstable family, absent father, dominant mother.

“It really requires a perfect storm of factors for someone to act on those impulses,” says Michael Arntfield, director of the Murder Accountability Project, a nonprofit organization that tracks unsolved homicides. “We know that some offenders have diminished frontal lobe activity in their brain, where empathy and impulse control are regulated.”

However, serial killer Ted Bundy, who confessed to killing 30 young women in the 1970s, reported having an uneventful childhood. There are conflicting reports as to whether his brain was ever scanned for abnormalities.

In a 2013 progress report, Forrest described his relationship with his father as being normal and positive. Forrest said he came from a middle-class family and that his parents were law-abiding role models. He graduated from Fort Vancouver High School in 1967 with honors and lettered in cross country and track.

And, yet, Forrest admitted to sexually assaulting 11 women and girls, peeping on another woman and watching a group of girls swim nude. He’s only admitted to killing one victim.

Attendees of the FBI’s Serial Murder Symposium concluded that “the most significant factor is the serial killer’s personal decision in choosing to pursue their crimes.”

“Somewhere in those cocktail of things that’s where you get serial killers. … We don’t know what the ‘X factor’ is. I haven’t ruled out old fashioned biblical evil,” Vronsky said. “Some things we don’t understand and may never understand.”

Serial murder peak

Eighty-three percent of 20th-century serial killers made their appearance between 1970 and 1999, according to Vronsky. Radford’s data shows a peak in 1987, when there were 189 active serial killers. The Murder Accountability Project’s algorithm agrees there were far more suspicious clusters of murder in the late-1970s and ’80s.

“First of all, the phenomenon didn’t really have a name or was recognized as a national problem,” said Thomas Hargrove, founder and chairman of the Murder Accountability Project. “Evil inclination tends to flourish in darkness. Without knowing it’s a problem, it can exist happily, and it did.”

FBI agent Robert Ressler is believed to have coined the term “serial killer” while profiling violent offenders in the 1970s, though it didn’t appear in media until a 1981 New York Times report, Vronsky said.

When asked about potential causes for the peak in serial murder, Hargrove said the sexual revolution of the 1960s spawned a time of experimentation.

“A period of sexual freedom and exploration would not prevent a serial killer from exploring his feelings and playing in those dark realms,” he said.

Vronsky said the answers may lie in the killers’ childhoods — the baby boom era following World War II. As he read serial killers’ biographies, he noted similarities in familial breakdowns.

“You have a generation of (Great) Depression survivors, and you have some million men who had seen combat returning with all of this trauma, and it’s not being acknowledged,” he explained. “The dominant mother also begins to develop. You have a generation of mothers who lost husbands in the Great Depression or WWII, raising families as both father and mother.”

Vronsky also points to virulent rape literature being sold mainstream on magazine stands. True crime and men’s adventure magazines persisted in the 1980s and featured photos of abducted women bound, tortured and sexualized. These magazines scripted how serial killers do their killing, he said.

“A lot of serial killers have reported being obsessed with these magazines,” Vronsky said. “It gave them a scenario for which they expressed these primitive impulses sparking in their brain.”

Arntfield said he believes serial murder has remained relatively stable over the years. The so-called serial murder peak produced the most infamous killers — true crime hits such as Bundy, John Wayne Gacy and Jeffrey Dahmer.

“The first offenders, and some of the most grisly, crystallized what the public understands serial killers to be. It doesn’t mean there was an abundance of them then. There’s more of them than we think, and we’re linking the crime later in the series,” he said.

Arntfield said there are at least 30 serial killers that should be actively sought right now.

Road to justice

Identifying serial murderers is getting easier, even decades after the crime, thanks to significant improvement in laboratory testing of forensic evidence.

Modern DNA testing allows for smaller samples to be analyzed, and it produces more precise results. National databases link biological evidence for known offenders and unsolved crimes. DNA profiles can be obtained from offenders, crime scenes, unidentified human remains and even voluntary samples from the families of missing people.

“A lot of serial killers from the ’70s are being apprehended now because of DNA,” Vronsky said.

In 2014, investigators began reviewing evidence from Forrest’s past court cases to determine if any of it might be used in unsolved crimes. Forensic scientists with the Washington State Patrol Crime Laboratory identified a partial DNA profile found on an air pistol Forrest had used to torture a woman and discovered that the DNA belonged to “an unknown female source.” On Nov. 23, 2015, the DNA was matched to Morrison, whose remains were found Oct. 12, 1974, in Dole Valley.

The sharing of familial DNA is relatively new.

“Everybody is loading up their own DNA to find their long-lost second cousin. It has become a huge investigative tool in identifying victims, as well as suspects and securing evidence,” Vronsky said. “You no longer need the suspect’s DNA; you just need the suspect’s relative’s DNA. That kind of broadens the investigative scope of serial murders.”

It was genetic genealogy that helped authorities apprehend Joseph James DeAngelo, a 73-year-old former police officer who is suspected of being the Golden State Killer. DeAngelo, who was arrested in 2018, is believed to be behind a series of killings, rapes and assaults in the 1970s and 1980s in California.

Serial murders decline

Several experts interviewed for this story said serial murders are on the decline, due to advances in laboratory testing, the prevalence of video surveillance and cellphone use, as well as the improvement of interjurisdictional communication. Law enforcement also has a better understanding of the crime.

Moreover, Hargrove said, we live in an era of serial murder media overkill, and even that may have contributed to the decline.

“We’re starting to get a little smarter about identifying people who might become serial killers,” he said.

Radford University’s Serial Killer Database shows the number of identified serial killers had fallen to somewhere in the 40s in 2013 and 2014 — an about 80 percent decrease since 1987.

Aamodt thinks serial murder is on the decline because the overall murder rate is on the decline due to better policing and catching people after one kill.

“I think parole is a huge reason for the decrease,” he added. “When someone is convicted of murder, it’s now unlikely they will be paroled in a short time.”

Eighteen percent of serial killers who went to prison for a murder had been paroled and killed again, he said.

Forrest has been denied parole three times in the last decade. Countryman and Starr Lara, whose sister, Jamie Grissim, is Forrest’s suspected first victim, have staunchly protested his release. Countryman said she doesn’t believe Forrest is capable of hurting anyone now, but she says he doesn’t deserve to be released.

“And I will fight (his release) until my last breath,” she said. “The agony he’s put people through, the ongoing pain, I’m really angry about that.”

Experts say there’s also been a cultural shift in people’s behavior.

“We think it’s more difficult for serial killers to find a victim because people don’t engage in high-risk events like they did before, (such as) hitchhiking or walking to school,” Aamodt said. “When I think about what I did as a child, they would never let you do that today.”

Most of Forrest’s suspected victims were hitchhiking or walking when he encountered them.

He developed distortions that “hitchhikers are promiscuous, bad girls, it won’t hurt them as much,” a 2013 progress report states.