MARTINEZ -- After only about two hours of deliberations, jurors in Martinez Thursday found Darryl Kemp, a 72-year-old serial rapist, guilty of first-degree murder for the 1978 rape and murder of Lafayette mother Armida Wiltsey.

Jurors also found true the special circumstance allegations that Kemp killed Wiltsey, 40, in the commission of a kidnapping, that he killed her in the commission of a rape and that he had already been convicted of one murder before he killed Wiltsey.

The trial will move into a penalty phase beginning Tuesday morning, in which the same jury that convicted Kemp today will decide whether he should be sentenced to death for his crimes.

Wiltsey had been jogging around the Lafayette Reservoir on Nov. 14, 1978 when Kemp dragged her into the brush, tied her up with shoelaces, raped her and asphyxiated her, according to prosecutor Mark Peterson.

Wiltsey had attempted to fight off her attacker and managed to scratch him. At the time, though, the technology hadn't yet been invented to identify someone by their DNA and the murder remained unsolved for 25 years.

In 2003, the Contra Costa County Crime Lab reopened the case and found that the DNA under Wiltsey's fingernails belonged to Kemp, who was serving a prison sentence in Texas for raping three other women.

In 1959, 19 years before Wiltsey's murder, Kemp had been convicted of the 1957 rape and murder of Marjorie Hipperson in Los Angeles. At that time, he was also convicted of raping two other women in Los Angeles in 1957 and 1959.

Kemp was sentenced to death for Hipperson's murder, but his sentence was commuted to life in prison after the death penalty was declared unconstitutional in the mid-1970s.

He was paroled to Pleasant Hill in July 1978, just four months before Wiltsey's murder.