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Gary Ridgway left microscopic paint evidence on the clothing of several of his victims that went undetected for decades. Chelsea Stahl / NBC News

How a crime lab missed evidence that could have stopped the Green River Killer

Tiny paint spheres helped snare serial killer Gary Ridgway after at least 49 murders in Washington. The evidence was on his first victims, records show.

SEATTLE — For nearly two decades, one of the country’s most prolific serial murderers haunted the Pacific Northwest as a faceless specter of death, known only by his notorious nickname: the Green River Killer.

Even though a massive team of investigators had been assembled to track him down, the killer’s identity remained a mystery during the 1980s and ’90s, while dozens of girls and women disappeared from the streets around Seattle, only to turn up in wooded dumpsites months or years later as corpses or bones. 

Then, in late 2001, long after the case had turned cold and the killings seemed to have stopped, officials announced the arrest of a commercial truck painter named Gary Ridgway. They credited the big break in the case — what they said had singled out Ridgway from a pool of 1,300 possible suspects — to advances in DNA fingerprinting techniques that didn’t exist at the peak of the killings.

But an NBC News investigation shows the long-told narrative that forensic science had to catch up with the Green River Killer is false. 

Nearly 20 years before Ridgway was arrested, the Washington State Patrol Crime Laboratory overlooked key microscopic evidence found on the clothing of his very first victim — and of seven others who followed — according to interviews and a review of thousands of pages of documents obtained through public records requests. The tiny spheres of a unique industrial spray paint linking Ridgway to their murders could have been detected back in the 1980s, forensic scientists involved in the case recently acknowledged, possibly preventing at least some of his 49 confirmed killings.

Even some longtime investigators assigned to the case said in interviews that until now, they had been in the dark about the missed opportunity to catch the killer sooner.

“I’m appalled I didn’t know that that was even possible,” said Frank Adamson, a retired King County sheriff’s commander who supervised the Green River Task Force in the mid-1980s. “It would have been nice if we could’ve saved a life or two — or all of them.”

Gary Ridgway prepares to leave the courtroom after sentencing in Seattle in 2003. At right, members of the Green River task force comb a hillside near Kent, Wash., where Ridgway said he left a body.
Gary Ridgway after his sentencing in Seattle in 2003. At right, members of the task force comb a hillside where Ridgway said he had left a body.Josh Trujillo / Pool via Getty Images; Elaine Thompson / AP

Only after the DNA match that led to Ridgway’s arrest did a renowned trace evidence expert, brought in to help with the case, find the overlooked clues in 2003. The spray paint found on the victims’ clothing wasn’t sold to the public, and it was used only in the Seattle area on a wide scale in the early 1980s by Kenworth Truck Co., where Ridgway worked.

Authorities hailed the discovery publicly as another scientific breakthrough. It pressured Ridgway into confessing to 48 murders and leading detectives to four previously undiscovered bodies in exchange for sparing him the death penalty. 

But in a recent interview, the trace evidence expert, Skip Palenik, said he could have done the same analysis, with the use of an infrared microscope, back in the 1980s. And he almost had the chance, he said.

Palenik said that in 1985, when he visited the Washington crime lab to train staff members in discovering microscopic trace evidence, the director said he’d bring him into the case if investigators identified a suspect. 

But Palenik said the director never called. Seventeen years later, he said, “I get a phone call saying they want us to look at this case. And we ended up finding information that we could have found” back then.

Skip Palenik is reflected in a display case of microscopes at Microtrace LLC in Elgin, Ill.
Trace evidence expert Skip Palenik first heard about the Green River murders in 1985 while training forensic scientists in Seattle. Taylor Glascock for NBC News

Jeff Baird, the retired King County senior deputy prosecutor who led the prosecution of Ridgway and ultimately brought Palenik into the case, said in a recent interview he’d never heard about Palenik’s visit to the crime lab in the 1980s or knew the paint spheres could’ve been found then.

“It’s very conceivable that if those things had been more carefully examined at the time, the investigation would have taken an earlier, more productive turn that pointed directly to Ridgway,” Baird said. 

Asked about the overlooked evidence, a spokesperson for the Washington State Patrol Crime Lab said in an email that “with so much time having passed, we are reluctant to speculate on the mindsets and specific investigative strategies of past forensic leaders from so many years ago.”

Chesterene Cwiklik, the scientist who supervised the lab’s trace evidence work at the time, acknowledged in a recent interview, “We never looked at those really fine particles that Skip did.”

Sisters of Patricia Yellow Robe, Ridgway’s last known victim, said the revelations are upsetting but mean little now.

“If this would’ve been presented to us at a different time, there probably would be outrage,” Rona Yellow Robe said. “But there’s been a lot of time and space and healing that I wouldn’t want to give up to something that I can’t control.”

LuAnna Yellow Robe, left, and her sister Rona Walsh address Gary Ridgway in court in Seattle in 2003.
LuAnna Yellow Robe, left, and her sister, Rona Yellow Robe, at the 2003 court hearing where Gary Ridgway admitted to murdering their sister, Patricia.Elaine Thompson / Pool via Getty Images

1982-86: A decision about evidence

In July 1982, the body of Ridgway’s first known victim was pulled from the Green River in suburban Seattle, a pair of blue jeans knotted around her neck.

Embedded in the denim used to strangle 16-year-old runaway Wendy Lee Coffield were the tiny spheres of spray paint that would take more than two decades to detect.

After four more bodies were found dumped in and along the Green River within a month, the King County sheriff assembled a task force to track down a serial killer. 

The killer kept preying on vulnerable women and girls, many of whom were runaways or had been involved in street prostitution, leaving the bodies in remote, wooded stretches. Investigators compiled a list of hundreds of potential suspects and amassed a mountain of evidence from the dumpsites, turning much of the material over to state forensic scientists for analysis. 

Ridgway first came to the task force’s attention in 1983, when 18-year-old Marie Malvar disappeared after she got into a pickup truck with a man on Pacific Highway South. Her boyfriend and pimp later spotted what he thought was the same truck in front of Ridgway’s house and reported it to police. 

Ridgway told a detective he knew nothing about Malvar’s disappearance, but he kept resurfacing in tips and brushes with sex workers over the next several months. He voluntarily spoke with detectives and acknowledged he’d been arrested before for soliciting a prostitute. He said he’d continued to routinely pick up girls working the street and had even encountered two of the killer’s presumed victims. But he denied having harmed them. In 1984, he agreed to take a lie detector test — and passed.

By then, the killer had left behind key microscopic evidence that could have helped unmask his identity, records and interviews show. Along with the jeans used to strangle Coffield, the paint spheres were trapped in the weaves of fabric eventually found with seven other bodies and bones, records show. A purple shirt. A pair of jeans. A black knit sweater.

Gary Leon Ridgway
Gary Ridgway in a booking mugshot after his arrest in 1982 for soliciting prostitution. King County Sheriff's Department, via AP

But with the volumes of evidence, the staffing constraints and the workload of other cases statewide, crime lab officials had to choose what evidence to analyze, said Cwiklik, the lab’s trace evidence supervisor at the time.

They opted to focus on analyzing hairs and fibers, which “usually would have been the most fruitful,” Cwiklik said in a recent interview.

The analysts assigned to the case “actually did an amazing job” of sorting, analyzing and comparing thousands of individual hairs, fibers and chunks of paint and other collected debris, she said. 

But focusing analysis on hairs and fibers meant the lab “basically ignored” smaller particles and dust on clothing and other items, Cwiklik said.

In early 1985, Ridgway drew suspicion again after another woman reported that a man who showed her his Kenworth employee identification card tried to strangle her after he had paid for sex in 1982. When a detective questioned him, Ridgway claimed he choked the woman only after she bit him. The woman declined to press charges, according to the detective’s report.  

The same year, Palenik, the renowned trace evidence expert, learned about the case. Palenik, then a senior researcher at the Chicago-based McCrone Research Institute — a leader in microanalysis — taught workshops around the country. He’d just finished teaching a basic forensic microscopy course at the crime lab in Seattle when George Ishii, then the director, told him about the Green River murders, Palenik said in a recent interview.  

Before he left town, Palenik said, Ishii vowed to seek his help if a suspect emerged. But he never heard about the case again from Ishii, who died in 2013. Ridgway is known to have killed at least four women after 1985, when Palenik visited Seattle. 

Microscopic slides of various materials sit on the desk of Skip Palenik at Microtrace in Elgin, Ill.
Microscope slides with various materials on Skip Palenik's desk at Microtrace.Taylor Glascock for NBC News

“Imagine in ’85, after I was out there, if George sent this stuff back to us, we’d find and identify the spheres as this unusual urethane paint,” Palenik said. “And then when they bring in a suspect and it’s Gary Ridgway — well, where does he work? He works at a place where he sprays the very same unusual paint on trucks all day.”

But without that forensic testing, Ridgway slipped through investigators’ grasp and kept killing. 

1987-90: ‘We should have done it’

By 1987, Ridgway’s penchant for prostitutes and past brushes with known victims and other tips were enough to help investigators get a warrant to search his home, vehicles and workplace.

In an affidavit, investigators wrote that they wanted to compare trace evidence collected from various dumpsites that might be tied to Ridgway, including green polyester carpet fibers and aluminum fragments.

But the hair, fibers, clothing and other evidence that were seized didn’t definitively tie Ridgway to any victims, and he slipped back into the slush pile of suspects as the decade ended.

In hindsight, Cwiklik said, the crime lab should have shifted its focus from hairs and fibers and turned to analyzing smaller particles in the trace evidence recovered from the dumpsites.

By 1990, Cwiklik said, the crime lab was using an infrared microscope, capable of detecting finer details than an optical microscope. For years, the lab also had been using techniques to capture smaller fractions of trace evidence that could have helped to detect the paint spheres, she said. But it still would have needed an outside specialist, like Palenik, to identify and trace them back to their source, she said.

“Really, we were capable of finding these things, but we didn’t because we didn’t look at the small, small fractions,” she said. “It always bugged me that we didn’t do that, but it would have been hard to argue that we should prioritize that.”

“But later on, when nothing was fruitful,” she said, “we should have done it.”

King County Prosecutor's Office via Getty Images)
Investigators search for the remains of one of Gary Ridgway's victims.King County Prosecutor's Office via Getty Images

1990s: A rejected request

By the early 1990s, when a new wave of bodies and bones were found, the Green River Task Force had already disbanded. But a smaller group of detectives who feared the killer was still at work quietly kept the probe alive. They focused on a prime suspect: Ridgway.

In November 1992, detectives formally requested that the crime lab compare hairs collected from Ridgway to those recovered from the new wave of victims, according to a detective’s memo to the lab obtained through a public records request. But officials for the crime lab, which by then had spent years futilely analyzing hairs and fibers in the case, rejected the request as a pointless endeavor, retired King County sheriff’s Detective Tom Jensen said.

Jensen, who dedicated most of his career to the case, was stunned to learn recently from an NBC News reporter that the capability to detect the paint spheres that linked Ridgway to some of the victims had existed years earlier.

He couldn’t recall lab officials’ ever having mentioned to detectives that smaller particles of trace evidence hadn’t been analyzed, he said.

“I should think we would have done the testing if we knew about it,” Jensen said. “We were doing everything we could to come up with a shred of evidence.”

As the ’90s wore on, Jensen was left to investigate the Green River murders on his own as leads dried up.

Jensen’s list of the killer’s suspected victims grew to nearly 90, including dozens of homeless or drug-addicted girls and women who’d disappeared or were dumped in remote places across western Washington.

Near the end of the decade, the killings seemed to stop. But they hadn’t.

When Patricia Yellow Robe’s body was found in bushes outside a wrecking yard south of Seattle in 1998, she wasn’t considered a victim of the killer. The medical examiner ruled her death an accidental overdose.

Yellow Robe grew up in Montana as the oldest of nine siblings in a family splintered by alcoholism. By 38, she’d been in and out of rehab and had suffered chronic health problems. She spent her last days couch-surfing and frequenting dive bars, police records show. 

Patricia Yellow Robe.
Patricia Yellow Robe, the eldest of nine siblings, was a protective big sister and a talented seamstress who struggled with addiction.Courtesy LuAnna Yellow Robe

After Yellow Robe’s sisters viewed her body at the funeral home, they had doubts about how she died. “She looked beat up,” Rona Yellow Robe recalled, noting a bruise on her face. A deputy discounted it at the time, telling Rona the bruise was most likely a byproduct of her sister’s “lifestyle,” she said.  

2000s: Catching the killer

By 2001, improvements in DNA science allowed the crime lab to better analyze small and degraded genetic samples. That prompted Jensen to submit evidence collected from several victims’ bodies, along with a piece of gauze Ridgway had chewed on when the warrant was served in 1987.

With the new technology, scientists were finally able to match DNA from Ridgway’s saliva to sperm recovered from two victims found in the river in 1982 and another victim from a dumpsite in 1983.

Based on the results, Ridgway was arrested and charged with the aggravated murders of all three victims, as well as another found just feet away from the two in the river. He pleaded not guilty, claiming through his lawyers that he’d “dated” — but hadn’t killed — the victims linked to him based on his DNA.

As he prepared to put Ridgway on trial, Baird, King County’s lead criminal prosecutor on the case, enlisted several outside forensic labs in 2002 to help examine the mass of evidence in the case. By chance, Baird said, he “stumbled" on Palenik, who by then was running his own lab, Microtrace, which had worked on high-profile cases, including the Unabomber investigation and the Atlanta child murders.

Family members of victims confronted Gary Ridgway in court in 2003. From top right, Virginia Graham, sister of Debra Estes, Jose Malvar Jr., brother of Marie Malvar, and Carol Estes, mother of Debra Estes.
Family members of victims confronted Gary Ridgway in court after he confessed to 48 murders. From top right, Virginia Graham, sister of Debra Estes; Jose Malvar Jr., brother of Marie Malvar; and Carol Estes, mother of Debra Estes.Pool via Getty Images; EPA

For the next several months, Microtrace analyzed paint gathered from Ridgway’s home, workplace and vehicles to create a reference library and then compared it with paint fragments collected in or around the dumpsites where victims were found. Nothing matched.

So Palenik decided to change tactics: vacuuming the dust from the suspect's and the victims’ clothing and analyzing the tiny particles under a microscope equipped with an infrared device used to detect colors and compositions of substances.

Since the late 1970s, Palenik had been routinely using the vacuuming process with such infrared instruments to find and identify tiny particles that helped investigators crack cases, he said. In 2003, he used the same techniques with modern versions of the tools when he analyzed Ridgway’s clothes and items found with 13 Green River victims.

After having vacuumed the clothing, he plucked the tiny particles captured in special vacuum filters and then used an infrared spectrometer to identify them as unusual multicolor paint spheres. He found the spheres on Ridgway’s clothes and clothing from five of the victims. They matched.  

Palenik soon determined the glossy acrylic urethane spheres were air-dried droplets of a distinct commercial automotive spray paint, made by DuPont and called Imron.

Paint spheres discovered in the clothing of some of Ridgway's victims.
Trace evidence expert Skip Palenik discovered these tiny spray-paint spheres in the dust he vacuumed from the clothing of some Green River victims.Microtrace LLC

Chemists for the company later informed Palenik that DuPont had patented the high-end, specialty product and believed no one else in the world was making paint with Imron’s unique composition or pigments.

Some of the victims’ clothing had “dozens and dozens of these spray-paint spheres” in blue, green, red, orange and white, Palenik said. “And that’s just not normal.” It indicated the spheres came from a source that widely used DuPont Imron and in various colors, he said.

The paint wasn’t sold to the public in 1982, and Kenworth, where Ridgway worked, was “the only place in the Seattle area using this spray paint on a large scale in the early 1980s,” he said.

After Palenik informed Baird about his findings, prosecutors charged Ridgway with three more murders, catching his defense team off-guard.

One of his lawyers, Mark Prothero, later wrote in a book that even though his team downplayed the paint spheres, “the prosecutors couldn’t have found anything much worse for our client, short of a Polaroid picture of him strangling a woman.”

Baird recently described Palenik’s findings as “pivotal.” The paint spheres were “very, very powerful evidence” that, to Baird, was in many ways better than DNA because it was “not an arcane or highly technical forensic science but nevertheless very convincing on a gut level,” he said.

“These women were not employed at a paint store or involved in spray-painting activities, so the common thread was someone who was directly linked to Kenworth,” he said. “It’s just much more instinctive and accessible to a juror to make that connection. It’s just common sense.”

Skip Palenik in his office at Microtrace in Elgin, Ill.
Trace evidence expert Skip Palenik's discovery pressured Ridgway into admitting he was the Green River Killer. Taylor Glascock for NBC News

Soon after the additional charges were filed, defense lawyers approached prosecutors with a proposal. Ridgway would agree to confess to as many killings as he could remember having committed in King County and secretly help investigators find more victims if prosecutors spared him a death sentence.

Palenik said Baird called and confided: “‘You can’t tell anyone about this, but what if I told you that based on your report, Ridgway confessed to being the Green River Killer?’”

Gary Leon Ridgeway
After agreeing to a secret plea deal, Gary Ridgway took investigators to several remote sites where he said he'd dumped his victims' bodies.King County Prosecutor's Office via Getty Images

Over the next five months, Ridgway detailed his slayings and led detectives to the remains of four victims, including Malvar, the teenager whose disappearance in 1983 first alerted police to him. After a detective sent Palenik more clothing items, he found the paint spheres tied to three more victims, bringing the total to eight.

Ridgway told detectives that paint sometimes covered his face and work clothes when he sprayed it on the cabs of semi-trucks at Kenworth. He often went “patrolling” for sex workers right after work, he said.

Sometimes, he’d gone to lengths to evade detection, including clipping the fingernails of victims who had scratched him before he dumped their bodies. But he left behind some of his victims’ clothing, discarded at dumpsites or wrapped like ligatures around their necks. “They were just rags to me,” he told detectives. “Just rags.” 

In November 2003, King County Prosecutor Norm Maleng announced the plea deal that sent Ridgway to the Washington State Penitentiary in Walla Walla, where he is serving 49 life sentences. (Ridgway, 74, didn’t respond to an interview request sent in a letter to him in prison.) 

Without the deal, more than 40 of Ridgway’s murders most likely would have gone unsolved, Maleng said.

Among them was the murder of Yellow Robe, the last woman Ridgway said he could remember having killed. 

2023: Learning the full truth

Patricia Yellow Robe’s sisters had mourned her loss back in 1998, when they were told she’d overdosed. 

But they still privately questioned how Trisha — the family peacemaker who had aspired to be a seamstress, sang Supremes songs off-key and snorted when she laughed — really died.  

They finally learned the truth from a newspaper reporter’s phone call in late 2003.

At first, LuAnna Yellow Robe said, she thought the caller had dialed the wrong number. Trisha died of an overdose five years earlier, she told him.

Until that day, prosecutors had kept the details of Ridgway’s confession secret even from her, a paralegal in their office. 

The truth was her sister was strangled and was counted as the last of Ridgway’s victims.

When her anger and shock wore off, her family’s doubts about Trisha’s death finally made sense, LuAnna said.

Patricia Yellow Robe's sister, LuAnna, left, and Rona.
“She wanted us to know the truth," said Patricia Yellow Robe's sister, Rona, right, standing with another sister, LuAnna.Jovelle Tamayo for NBC News

After Ridgway confessed, the medical examiner’s office acknowledged that, despite toxicology results that detected large amounts of opiates and alcohol in her bloodstream, it may have missed signs that Trisha had been strangled.

“She wanted us to know the truth,” Rona Yellow Robe said, “and I’m glad I know it.”

That truth, LuAnna and Rona recently learned from an NBC News reporter, now includes another detail: about the tiny, overlooked evidence that could have tied a killer to his crimes long before he ever murdered their sister.

“Does it make me angry?” LuAnna asked. “It’s too bad they didn’t do what they should have done. But being angry now won’t bring my sister back.”