DENVER (AP) Authorities all along had the DNA evidence to link a convicted a triple-murderer to four additional murders, and they say he could have been responsible for as many as 20 slayings.

But the process of developing an identifying DNA " fingerprint" was still five years away when authorities say Vincent Groves killed a prostitute, a banker, and a store clerk in 1979.

By the time Groves had been let out of prison in 1987 and went on a suspected killing spree that left police discovering a body a month in and around Denver for about a year, authorities were still struggling with how to handle DNA. Colorado was the first state to require DNA but only from sex offenders in 1988 and the FBI's national database was a decade away from becoming fully operational.

On Wednesday, Denver District Attorney Mitch Morrissey announced that through federal grants for a cold case unit in the Denver Police Department and his office, four slayings had been solved though DNA matches.

Groves, who died in prison in 1996 at age 42, was tied by DNA to the 1979 killings of women found strangled and partially nude in an alley, an industrial park and a bathtub in Denver. Police used a DNA profile of Groves they recently found from an old murder investigation and linked it to the four separate crime scenes, authorities said.

"So often times, a serial offender can fly below the DNA radar screen, maybe leaving DNA, but because their criminal history occurred at a time when they weren't eligible to go into the database or there was no database, they stay at large continuing to commit their crimes," Morrissey said.

The 1979 slayings of Emma Jenefor, 25; a store clerk in a tony area of Denver; Joyce Ramey, 23, a suspected prostitute, and Peggy Cuff, 20, a banker, bore strong resemblances to Groves' past killings and the disappearance of a woman that Groves was suspected in, authorities said. Police also linked Groves to the 1988 strangulation death of Pamela Montgomery, 35, a suspected prostitute found dead in an alley.

Groves would target women he knew who were addicted to cocaine or prostitutes he picked up on Colfax Avenue, a street in Denver historically known for prostitution, said Morrissey and Mylous Yearling, cold-case investigator for Denver's police department.

Groves strangled most of his victims; many were found nude or partially clothed, left in the mountains west of Denver, alleys and fields outside the city, police said.

When he died, Groves was serving a life sentence for the 1980s strangling of two young women. He had been released on parole in 1987 after serving five years in prison for killing a third woman in suburban Denver.

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DNA tests link convicted killer to 4 Denver deaths