A former California state mental hospital director was found guilty Thursday of sexually abusing his adopted son in what prosecutors contend was a pattern of preying on young boys that spanned four decades.

A Superior Court jury convicted 63-year-old Claude Foulk of 31 of 35 counts of sex crimes, including lewd and lascivious acts on a child and sodomy by use of force.

Foulk did not show any reaction as the verdict was read.

He was found guilty of 20 counts of forcible oral copulation, nine counts of sodomy and two counts of lewd acts. He was found not guilty of two counts of sodomy and two counts of oral copulation, charges that were alleged to have happened after the son turned 18.

Prosecutors say another 11 men also came forward to claim Foulk molested them as children dating back to 1965, but only the son's case could be prosecuted because of the statute of limitations.

Foulk was fired from his post at Napa State Hospital after his arrest last year.

He could face a maximum sentence of up to 248 years in prison when he is sentenced Feb. 23.

During an emotional weeklong trial, five now-grown men testified that Foulk abused them for years. They claimed the man they knew as an uncle and foster father bought them pizza and took them to a mountain cabin before forcing them to engage in sex acts.

One of Foulk's two adopted sons told jurors Foulk abused him from the time he was 9 until he was 21, telling him it was how a man shows love.