Derks confesses to 1985 rape and murder 

Peter Derks, the Arroyo Grande landscaper law enforcement investigators linked to a 20-year-old murder in Montaña de Oro State Park, has pleaded guilty and now faces life in prison without parole.

Derks, who would have faced the death penalty had he gone to trial, was arrested last year after semen and other biological material found at the crime scene - and stored for 18 years in a sheriff's department evidence locker - was matched to Derks' DNA.

In July this year, his lawyers attempted to convince Superior Court Judge Dodie Harmon of the need for a special hearing on the scientific validity of the process state investigators used to test the crime-scene DNA. Harmon turned down their request, thereby setting the stage for a possible trial later this year.

Instead of a trial, Derks pleaded guilty this week to three charges in the death of Mary Waterbury: premeditated murder, forcible oral copulation, and rape. Derks faces a sentencing hearing on Nov. 7.

In 1985, Mary Waterbury lived in a Stenner Street apartment with her sister. She was a liberal studies major at Cal Poly but was taking the fall quarter off to work as a bookkeeper. Coworkers would later describe the freckled 5' 4" softball player as "a little shy."

The afternoon of Oct. 19, she drove to Montaña de Oro in her sister's yellow Volkswagen Bug but never came home. Medical officials would later find that she had suffocated in the loose earth of the park while being raped. Years later, investigators revealed that Derks was one of their prime suspects at the time, but the district attorney lacked the evidence to charge him.

Two years after Waterbury's murder, however, investigators had enough evidence to charge, and later convict, Derks after he attacked another woman at Montaña de Oro.

Julie Richter was collecting shells in a jar as she walked on the beach near sunset in January 1987. Darkness was falling and Richter was following a trail up from the beach when she saw Derks standing on the top of a nearby dune. In court a few months later, Richter recalled that, as Derks approached her, she saw what looked like a "policeman's club" in one hand, and as he stopped in front of her, he raised the club in front of him.

"He said, ‘If you don't do everything I will tell you I'm going to beat the living shit out of you,'" Richter later said in court.

Richter, who was 5 feet 6 inches tall and weighed 106 pounds, said she threw her jar of shells in his face, ran, tripped, and fell to her hands and knees. Turning around, she saw Derks, his face covered in blood, almost on top of her and so she threw a fistful of sand in his face, scrambled to her feet, and ran to safety.

As part of a plea bargain, Derks pleaded guilty to the charge of assault with a deadly weapon and was sentenced to nine years in state prison.

That wasn't only time Derks spent time in prison for violence against a woman. In Texas in 1973, he was convicted of raping a woman at gunpoint, and served 11 years of a 30-year sentence.

In San Luis Obispo court years later, Derks would admit that he had "difficulty forming relationships with women and acknowledged that although he needed counseling, he had failed to take advantage of the counseling available during his incarceration in Texas."

- A.H.