Part II: Two Seattle Cold Cases

With more than 300 old unsolved murders, Det. Richard Gagnon and Det. Greg Mixsell are hunting for suspects wherever the clues take them.

That's how they cracked the biggest case of their careers - the 10-year-old murder of singer Mia Zapata. And now, Florida fisherman Jesus Mezquia sits in jail, awaiting trial for the Mia's murder.

But before they find out if there will finally be justice for Mia, the detectives have another case to solve -- the brutal murder of 13-year-old Kristen Sumstad -- and they are raising troubling questions about the boy who lived next door.

Athan is now a 36-year-old married business owner with no record of a serious crime. But for the past 22 years, he may have gotten away with murder.

"At the time, he was a 14-year-old kid, and I honestly think that back in 1982, detectives never considered a 14-year-old kid would do something like this," says Gagnon.

Sumstad was a popular seventh grader who was the youngest of four sisters. On Nov. 11, 1982, Kristen was raped and strangled, and then left in a trash heap behind a TV repair shop.

"Denial is pretty powerful. It's clear that he had totally put Kristen Sumstad out of his mind," says Seattle prosecutor Steve Fogg. "And I think were it not for the DNA, that would continue to be the case until he died."

Gagnon and Mixsell again discovered DNA evidence -- in this case, semen left on Sumstad's body. But there was no match for the DNA in the FBI's criminal database -- which meant her killer has never been arrested for a serious crime.

"During the course of our investigation a name kept coming up. John Athan," recalls Gagnon.

But the first real break in the case came when Gagnon and Mixsell discovered that Athan was seen near Magnolia TV - pushing a cart with a large box on it - on the night Kristen's body was dumped.

The Cold Case Squad's next job was to find a motive. And Kristen's friend Kim Alguard provided one. "We always seemed to run into him, whether it was at my house or her house or the village. He always seemed to be around," recalls Alguard. "He never approached me, he always approached her. Everything was always addressed to Kristen, looking at Kristen, talking to Kristen, like I was a ghost."

Discovering where Athan lived, however, was only half the solution. The real challenge was getting a sample of his DNA, without him knowing about it.

"We had to try to get some way to get the sample to come to us instead of us go to it," says Gagnon.

What the detectives came up with cost just 37 cents: the price of a stamp. They sent Athan a letter written from make-believe lawyers, inviting him to make some money by joining a lawsuit over parking tickets.

Why did the detectives think a class action suit would work with this particular suspect? "He's a male. There's two things that males will cave into: sex or money," says Gagnon. "And he bit. He figured easy money."

Athan mailed his response a few weeks later. "I got a phone call from Det. Gagnon and he said, 'Can you get DNA from an envelope flap?' And I said, 'Yeah, you bet,'" recalls forensic scientist Bev Himick, who extracted DNA from the saliva Athan left on the envelope when he licked it shut.

Then, she compared it to the DNA from the semen found on Kristen Sumstad's body. "When I put the two together, wow. It was a match," says Himick.

"I'm believing he's playing right into our trap. We want either a full confession or total denial," adds Gagnon. "If he'd have said, 'Oh yes. We were boyfriend/girlfriend and I'd had sex with her once a week,' it would be difficult at that point. But he says, 'Barely know her.'"

Gagnon and Mixsell booked Athan for murdering Kristen 22 years ago. His reaction, according to Gagnon, was nothing. "Very unusual for someone to not attempt to explain something," adds Mixsell. "To ask some question. To plead innocence. This man did not do that."

To prosecutor Tim Bradshaw, it looked like an open-and-shut case. "He certainly sealed his fate when he sealed that envelope."

For Kristen Sumstad's family, the biggest shock of all has been finding out that Kristen's alleged killer is a former childhood friend.

"I freaked. This is someone I knew," says Kristen's sister, Jorgine. "This was a friend of mine. And I didn't have a clue."

Now, Cold Case prosecutors Tim Bradshaw and Steve Fogg are trying Athan for first-degree murder. He is being tried as an adult, even though he was just 14 when Kristen was murdered. If convicted, he could go to prison for life.

"Finally in March 2003, 21 years after Kristen Sumstad had been murdered, John Athan made a mistake. John Athan licked the envelope," says Fogg.

When Athan licked that envelope and mailed it to Gagnon and Mixsell, he gave them the key evidence against him — his DNA.

But Athan's attorney will argue that the DNA is not proof of murder. "The DNA evidence shows that at some point John and Kristin had sexual intercourse," says defense attorney John Muenster. "The prosecution has to prove that he killed her, not that he had sex with her."

Muenster puts the Cold Case Squad on trial, charging they illegally obtained Athan's DNA: "The sending of the letter really posed as a threat to the integrity of our legal system, because police cannot be permitted to pose as lawyers."

Muenster also charges that the Cold Case Squad tricked Athan into answering their questions.

Himick testifies that the odds are overwhelming that the DNA is Athan's: "It was 1 in 59 quadrillion," she says.

Prosecutors also present testimony to show their case isn't just about sex, it's about murder. First, Athan is forced to listen to a voice from his past, as Kristen's friend, Alguard, testifies that he pursued Kristen.

Then, Gagnon testifies that when the Cold Case Squad found Athan in New Jersey, he lied to cover up the murder.

And prosecutors made sure that day after day, Athan was forced to sit in front of the empty box where Kristen's body was dumped.

"He's seen it before. He decided to make an innocuous piece of garbage a cardboard coffin for a 13-year-old girl who weighed 87 pounds," says Bradshaw. "Maybe this'll help refresh his recollection."

They hope Athan will buckle under the pressure and it works. He repeatedly loses his temper and even confronts the judge over some of her rulings. The jury takes just four hours to reach a verdict. Athan is found guilty of second-degree murder, and he's defiant as he's taken away.

After 22 years of freedom, Athan is finally being held accountable for Kristen's murder. Athan is sentenced to 10 to 20 years in prison. And the punishment is relatively lenient because he was just 14 when he committed the crime.

Even as the trial begins, Mixsell and Gagnon are still investigating Mezquia, and they're now convinced he never met Mia Zapata until the night of her murder.

"He was always looking for a victim," says Gagnon. "He was a predator."

They've also discovered Mezquia has a record of assaulting women, including his wife. But the heart of the case against Mezquia is a tiny bit of saliva that was swabbed from Mia's breast. Cold Case prosecutor Tim Bradshaw tells jurors that the saliva, and the DNA it carries, is all the evidence they need.

"The evidence that was previously left in darkness has been illuminated and exposed to the light of the laboratory and will be exposed for your consideration in the light of this courtroom," says Bradshaw.

Mezquia, a Cuban, listens to the trial through translators, but he never speaks and never takes the stand in his own defense.

His attorneys try desperately to argue that the presence of his saliva does not prove he either raped or killed Mia. They also try to argue that the DNA was corrupted at the crime scene, that the DNA was somehow ruined by paramedics trying to revive Mia, and that Mezquia's DNA may not have originally been on Mia's breasts.

Day after day of testimony about Mia's death is taking its toll on her father. "It just wears you down mentally," says Dick Zapata. "There's no room in your life for anything else."

Mercifully, the trial concludes after just eight days, and the detectives and Dick Zapata are confident of victory. "I can't see 12 people walking this guy. I mean that would probably be the biggest travesty of my career," says Gagnon.

The jury does something completely unexpected. They deliberate for three days, and tensions start running high. Then, on the fourth day, the jury reaches a verdict for Mezquia: guilty. His punishment is severe: Mezquia will serve 37 years in prison, well above the state's normal sentence for first-degree murder.

"I think justice is served," adds Gagnon. "We got the right verdict."

And with two of their toughest cases now finally put to rest, the Seattle Cold Case Squad has a message for anyone out there who thinks they got away with murder.

"The clock's always ticking. You're not a free man," says Gagnon. "Maybe someday on the road, there'll be a knock on the door. If you're having trouble sleeping at night, I think we've done our job."

In the Mia Zapata case, the FBI's DNA data bank was critical in tracking down the killer who had walked free for nearly a decade. It's worth noting that Rhode Island and Mississippi recently joined the system. So now, all 50 states are linked to it.

And while there are some legal challenges to the FBI data bank, it continues to grow and states keep expanding the types of crimes where DNA is being collected.