The unanimous decision overturned an earlier ruling by a state appeals court.
That court reversed the conviction of Fernando Lopez after finding that the prosecutor erred during his trial by expressing her personal opinion to the jury.
The case now goes back to the state appeals court.
Lopez, a Colombian citizen, was convicted of molesting three boys over three years at St. Thomas the Apostle Parish and sentenced to nearly seven years in prison in 2005.
The case marked Los Angeles County's first successful prosecution of a Catholic church clergy abuse case after the U.S. Supreme Court struck down a California law that had lifted the statute of limitation in old molestation cases.
At the time of his arrest, Lopez was a visiting priest in the Archdiocese of Los Angeles, which suspended him.
In his appeal, Lopez argued that the prosecutor made inappropriate comments by telling jurors: "I don't think (the defense attorney) is mean or stupid. But I think his client is guilty."
The high court wrote that the prosecutor based her statement on evidence she had presented and noted that the defense attorney did not object to the comment at the time.
Lopez's attorney, Mark Lenenberg did not return a call or e-mail seeking comment. Deputy Attorney General Michael Katz said he was "very gratified."
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