MISSOULA, Mont. -

A Missoula man with a previous conviction for sexual assault has been sentenced to 15 years in federal prison in a child pornography case.

The U.S. Attorney's Office says 51-year-old Douglas Robert Brooks was sentenced Thursday by U.S. District Judge Donald Molloy in Missoula. He also was sentenced to spend the rest of his life on probation.

Brooks earlier pleaded guilty to accessing with intent to view child pornography. He was convicted of sexual assault in 2000.

Prosecutors say an informant notified a probation officer last November that Brooks had child pornography on a computer. Officers with a search warrant seized a computer and a thumb drive that contained images of child pornography.