SACRAMENTO (AP) — A Yuba City man who was once known as the nation’s worst serial killer was again denied parole Monday after he admitted his guilt for the first time before the parole board.

Juan Corona said he murdered and mutilated 25 farmworkers four decades ago because they were trespassing in the orchards north of Sacramento, said Sutter County Assistant District Attorney Jana McClung.

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Parole officials decided Corona can try again in five years, McClung said after the two-hour hearing. It was Corona’s seventh bid for parole from Corcoran State Prison.

Corona previously made incriminating statements to a prison psychologist but had never before acknowledged his guilt during a parole hearing.

“This is the first time that I’m aware of that he made that admission to the full board. He said it was trespassing and they were winos,” McClung said.

Corona, 77, has been diagnosed with dementia and mental illness.

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No family members of his victims attended the hearing. Prosecutors said Corona targeted victims who had few relatives and likely wouldn’t be missed.

“We have had no contact with survivors for two decades now,” District Attorney Carl Adams said before the hearing. “The people who he killed were farm laborers who were itinerant. Most of them didn’t have relatives who could be contacted back in the ’70s at the time of trial.”

Four of the bodies have never been identified. The bodies of 14 of Corona’s victims were never claimed by family members after they were discovered in 1971.

Corona was tried in Colusa County and was found guilty of first-degree murder in January 1973 and received by the California Department of Corrections and Rehabilitation on Feb. 17, 1973. His conviction was overturned on appeal in 1978, and he won a new trial.

In 1982, Corona was again convicted of all 25 murders and sentenced to 25 life sentences.

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(Copyright 2011 The Associated Press.)