LAPD detectives found a killer -- just not the one they were looking for

By the time homicide Det. Dennis Kilcoyne met with Diane Webb last fall to discuss the maddening search for a serial killer who has stalked South L.A. for decades, he was wide open to suggestions. Despite more than a year of chasing leads, Kilcoyne and his team of detectives were no closer to catching the man suspected of sexually assaulting and murdering at least 10 young black women.

Webb, who heads a Los Angeles Police Department unit responsible for tracking the whereabouts of sex offenders, suggested a new tack: Though most of the roughly 5,200 sex offenders registered in Los Angeles comply with a requirement to submit DNA samples to authorities for input into state databases, many have slipped through the cracks. The officers in Webb's group fanned out across the city to track down men who possibly fit the killer's profile and to collect DNA samples for comparison to evidence left behind by the killer.

The plan worked.

Just not in the way Kilcoyne had intended.

In late March, the California Department of Justice's DNA laboratory jolted LAPD detectives with news that the saliva collected from 72-year-old John Floyd Thomas Jr., one of the sex offenders contacted by Webb's officers, matched genetic evidence found at the crime scenes of two Los Angeles women raped and killed in the 1970s. Soon after, Thomas was tied by DNA to three more slayings. Details from those cases matched dozens of other unsolved murders and rapes. The women, however, had been older and white, not black and young.

And Thomas' DNA didn't match the man Kilcoyne was hunting.

In looking for one serial killer, the LAPD believes it has stumbled upon another.

The capture of Thomas was one of the biggest by California law enforcement in recent years. Police suspect he is the "Westside Rapist" -- the man who late at night terrorized upscale neighborhoods on the city's Westside in the 1970s, breaking silently into the homes of women who lived alone and raping and strangling them. The violence stopped when Thomas was sent to prison for a rape and started again in Claremont a decade later, shortly after Thomas was released and moved to the area, according to police. At the time of his release, authorities did not keep DNA databases.

Thomas is scheduled to be arraigned in August on two murder charges. LAPD Det. Richard Bengston, who is handling the case with his partner, acknowledged in an interview that DNA evidence from several of Thomas' other suspected crime scenes is not as definitive, but said he expects the LAPD and the L.A. County Sheriff's Department to file additional murder charges.