A Kirkland man pleaded guilty to receipt of child pornography in U.W. District Court in Seattle Thursday.

Robert Francis Pierce, 41, has prior convictions for first degree child rape and molestation in Snohomish County.

Pierce faces a mandatory minimum 15 years in prison when sentenced by U.S. District Judge Marsha J. Pechman on May 14.

Federal investigators traced child pornography to an internet address associated with Pierce last May, according to court documents. Law enforcement searched Pierce’s Kirkland apartment and agents located two computers containing more than 600 images of child pornography in August. Some of the images found were of children appearing to be as young as 9 years old.

Pierce admitted that he downloaded the images using Peer to Peer software. He told officers he looked at child pornography because he is bored and finds it thrilling, according court papers.

Pierce was previously convicted of first degree child rape and molestation in Snohomish County in June 2003. He was sentenced to 131 months in prison, with all but six months suspended.

That suspension will now be revoked and Pierce is expected to serve the remaining state sentence concurrently with the federal sentence. In the federal case, both the defense and the prosecution will recommend a sentence of 15 years in prison.

The case was investigated by the FBI and was prosecuted by Assistant United States Attorney Michael Scoville.