(CBS/AP) SACRAMENTO, Calif. - A California man who was once the nation's worst known serial killer is up for parole, four decades after the mutilated bodies of 25 farmworkers were unearthed in orchards north of Sacramento.
Juan Corona, 77, who's been diagnosed with dementia and mental illness, is making his seventh bid for parole from Corcoran State Prison in the southern Central Valley.
None of the victims' relatives were expected to attend Monday's hearing, which Sutter County District Attorney Carl Adams said is a sad testament to Corona's crimes, which targeted people who had few relatives.
"We have had no contact with survivors for two decades now. 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," Adams said.
Four of the bodies were never 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, 40 miles north of Sacramento.
His first conviction in 1973 was overturned on appeal, but he was convicted again in 1982 and sentenced to 25 concurrent life sentences.
It was the worst known killing spree in U.S. history, until John Wayne Gacy Jr. was convicted in 1980 of murdering 33 young men and boys in his Chicago home. Gacy was executed in 1994 in Illinois.
Investigators found a machete, a meat cleaver, a double-bladed ax and a wooden club, all stained with blood, in Corona's home, along with a ledger book containing the names of seven of the victims.
Corona, a Mexican national and native of Jalisco, Mexico, has maintained his innocence, though at an earlier parole hearing he acted confused and told the parole board he didn't recall much. His attorneys have argued that his mental and physical condition make him less dangerous.
Adams said his deterioration makes him a greater threat to himself and others.
"He is unreliable dangerous. He's also old and not in a condition where he can do well on the streets without prison supervision," Adams said. "Releasing him into the public wouldn't be doing him any good or the public any good."