The slayings of a Goleta couple 30 years ago have been linked through DNA evidence to an unidentified man thought to be responsible for a string of rapes and killings in Sacramento, Ventura and Orange counties, Santa Barbara County authorities said Thursday.

The DNA finding confirms a long-held theory that the July 1981 slayings of Cheri Domingo, 35, and Gregory Sanchez, 27, were the work of a serial killer whose last known crime occurred in Orange County in 1986.

“With recent advancements in DNA profiling methods, it was important for us to push forward and reevaluate evidence in this case before it deteriorated and became useless,” said Santa Barbara County Sheriff Bill Brown.

Nearly 18 months after the slayings, another Goleta couple -- Dr. Robert Offerman, 44, and Alexandra Manning, 35 -- were killed in their condominium. Police believe -- but have not confirmed -- that the same person murdered both couples.

While investigators have enough to profile the killer -- dubbed the Original Night Stalker to distinguish him from Richard Ramirez, the serial killer known as the Night Stalker in the 1980s -- they do not know where he might be, if he’s still alive.

Santa Barbara County crime technicians analyzed more than 50 pieces of evidence in the slayings of Domingo and Sanchez. The samples, including a semen stain, yielded small amounts of DNA that had degraded over time. They were transferred to a law enforcement DNA lab in Richmond, Calif., and matched to samples from four cases involving the Original Night Stalker.

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-- Steve Chawkins

Photo: Domingo and Sanchez. Credit: Santa Barbara Sheriff's Department