They were found sprawled side by side on the living room floor by the woman's brother, who after a morning of flipping burgers at a nearby Burger King restaurant had just one thing on his mind: that night's festivities.

The couple looked to be snuggling or possibly sleeping off a hangover, Michael Richter, who was 16 years old on that Christmas Eve in 1998, told police.

And so he tiptoed to his room, past the tangle of legs jutting from the doorway between the living room and the kitchen in the couple's cozy apartment in northeast Minneapolis. The woman's sister arrived a short while later, with her 4-year-old daughter in tow, and reached a similar conclusion.

Hours passed before they discovered the grisly truth: The woman, Carrie Richter, and her boyfriend, Dustin Baity, had been murdered.

Nearly two decades would pass before the killer would be sentenced. The sentencing came last week, thanks in part to the determination of Sgt. Chris Karakostas, the latest in a succession of detectives to try his hand at solving the murders.

In 2015 Karakostas, working with another detective who has since retired, helped to revive the department's cold case unit, a collaboration with the Hennepin County attorney's office and the FBI to review unsolved murders, from the 1985 stabbing death of single mother Tina Slaughter to the slaying of 3-year-old Terrell Mayes Jr., who was killed by an errant bullet that tore through his north Minneapolis home in 2011. The so-called Cold Case Squad's website features sharply produced videos that encourage anyone with information to come forward.

Few cold cases end in arrest, and fewer still result in a perpetrator getting locked up. Police estimate that only 1 percent of cold cases get closed. But sometimes the odds can turn in investigators' favor.

Years later, a match

The Hennepin County medical examiner determined back in 1998 that Baity had died of ligature strangulation, while Richter suffered a far more gruesome fate. She had also been strangled, an electric cord still wound around her neck, but someone stabbed her in the face, torso and arms 37 times. Nearby lay a silver tray, covered with what preliminary DNA testing revealed was Richter's and Baity's blood.

There was no murder weapon in sight, but the room contained plenty of objects on which the killer might have inadvertently left fingerprints, so the case seemed promising.

Instead, things quickly cooled.

People were questioned and leads chased down. One led investigators to the streets of Duluth. Another pointed them to a person of interest who had been bragging around town of his involvement in the slayings. The man later died. And so it was, a decade and a half on, police were back where they started: with no suspect and no motive.

"That's when the case started to drift," Karakostas said last week.

Police officials said there wasn't enough evidence to charge anyone, and in the meantime new homicides were piling up that required detectives' attention. The Christmas Eve murders were just two of 58 homicides in Minneapolis in 1998, and the city recorded 48 the next year.

Changing hands

Over the years, the case file on the murders had been passed down from one investigator to another. Karakostas, then in the homicide unit, inherited it in 2007 from another detective who had tried unsuccessfully to reboot the investigation. Karakostas had a personal connection to the case. He was working that Christmas Eve when the call came over the scanner, and he still remembers walking into the bloody murder scene.

At the time, detectives checked the caller ID on the apartment's landline and the last number to appear on the screen matched a contact saved on Baity's cellphone: Jason Preston. Preston, detectives learned, had known the couple in passing, and he volunteered to come down to police headquarters for an interview. But without physical evidence tying him to the scene, investigators started considering other suspects.

Karakostas worked other cases as they came, often logging 80-hour weeks, but the murders were never far from his mind.

Every so often, he would drive down to the department's labyrinthine 32,000-square-foot storage warehouse in southeast Minneapolis, home to roughly half a million pieces of evidence from past homicides, rapes and robberies, and start going over the case again.

The first major break came in 2013.

Karakostas, acting on a hunch, sent some of the evidence to the state Bureau of Criminal Apprehension crime lab to be retested to see if he could generate some new leads. This time, the DNA results came back with a new hit — a speck of blood that forensic testing determined didn't belong to anyone who had been known to be in the room that night. It was on a silver tray found at the scene.

Karakostas flew out to Los Angeles to again interview Preston, who was serving a sentence in California for aggravated robbery after he and several others broke into a woman's home in Culver City and tied up her and her son.

"If you talked to him, you're not going to think the guy's a killer," he said. "He sits down, is very polite, you know, 'Yes sir, no sir,' that type of thing."

While Karakostas was in L.A., he spoke to one of Preston's co-defendants from the home invasion case who told the detective that Preston had bragged about getting away with the murders.

Months later, Karakostas' phone pinged with the results of a more definitive DNA test. The blood on the silver tray

belonged to Preston.

Decades later, justice

In many cold cases, victims can be nearly as elusive as suspects, said Steve Redding, a senior Hennepin County prosecutor who tried the Preston case. After reporting the crime, they often disappear or avoid police, he said, leading authorities to shelve their cases.

Improving DNA testing has helped authorities overcome reluctant witnesses. Investigators now can check available evidence against state and national databases, particularly in murder and rape cases, Redding said.

But like other crime-fighting tools, it's not foolproof, he said.

"It's still a very intensive investigative process, because DNA just tells you that somebody's DNA cells are there, it doesn't tell you much else," said Redding, who tried the first two so-called cold-hit rape cases in the country in the early 1990s. "Back then it took a dime-sized spot of blood, but now you're talking a couple of cells that you can't even see," he said recently.

Preston, still serving a prison sentence in the California home invasion when he was charged in the Minneapolis murders, admitted in court last November that he had been at Baity's apartment when an argument ensued over an unpaid drug debt. In his rage, he said, he strangled Baity with a cord, but insisted that he hadn't killed Richter, saying instead that he pinned her down while an unidentified assailant stabbed her to death — a disclosure that came as a surprise to prosecutors, who said Preston had never previously mentioned an accomplice.

Last week, Preston was sentenced to 48 years in prison.

Baity's sister, Dawn Baity, of Minneapolis, said Friday that Preston's sentencing brought the family some relief. But, she added, "It's kind of bittersweet.

"You know they wouldn't want you to be sad. You can decide to enjoy things twice as much," once for yourself and once for them, she said.

As for Karakostas, he is closing in on a suspect in one of the 10 cases he is currently juggling. "There's a good one coming," he said with a grin.

Visit the MPD's Cold Case Files website at insidempd.com/cold-case-files.

Staff researcher John Wareham contributed to this report.