Only one victim was named in the current case and jurors were unable to reach verdicts on four counts, so a mistrial was declared on those.
Wempe, 66, who was immediately taken into custody, agreed to waive sentencing until the district attorney can decide whether to seek a retrial on the undecided counts.
He faces a sentence of 16 months to three years on the single count. He has already served a year in prison, so that time would be deducted. One of his attorneys said he was diabetic and had a heart condition, so likely would serve his time in a medical unit.
The credibility of the victim, Jayson B., was attacked by the defense and his testimony was short on details and dates. During deliberations, jurors sent the judge many questions asking for more evidence and expressed skepticism about some of the acts described by the victim.
"I hope this brings some closure to the people involved," said Donald Steier, one of Wempe's attorneys.
Wempe's lawyers acknowledged that the priest molested 13 boys in the 1970s and 1980s, but said he went into church-ordered treatment and returned a changed man. Attorneys maintained he never molested anyone after that.
Wempe was spared trial on charges from the '70s and '80s when the U.S. Supreme Court upheld the statute of limitations on the crimes, but he did spend a year in jail before that ruling was issued.
Jayson B., the brother of two earlier victims, alleged he was abused from 1990 to 1995 when Wempe was a hospital chaplain.
"The prosecution's case was based on passion, prejudice and emotion for what happened 20 to 30 years ago," Wempe attorney Leonard Levine said. He said he believes Jayson B. was attempting to obtain retribution against the priest for molestation of his brothers.
Deputy District Attorney Todd Hicks, who described Wempe as a "hip" priest who wore his hair long, rode a motorcycle and gave such dynamic sermons that young people and their parents were drawn to him, said he was pleased with the verdict and Jayson was elated.
"I'm always happy when victims have their day in court," he said. He denied trying to appeal to the jury's emotions with testimony from eight long-ago victims, saying their testimony was used merely to show a pattern of behavior by Wempe.
As for the importance of the case, he said, "It sends a message to the archdiocese regarding this defendant. They certainly mishandled this defendant."