SACRAMENTO, Calif. - A California man 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.

Parole officials decided that Corona could 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, 77, previously made incriminating statements to a prison psychologist. But "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. "He just doesn't seem to realize that what he did was wrong."

Corona has been diagnosed with dementia and mental illness.

No family members of his victims attended the hearing. Prosecutors said Corona targeted victims who had few relatives and were unlikely to be missed.

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, a farm labor contractor with a history of mental illness, was convicted of stabbing the men, hacking open their heads and burying their remains near Yuba City.