A former University of Wisconsin student was found guilty of two counts of sexual exploitation of a child and eight counts of possession of child pornography last week.

Dane County District Attorney Robert Kaiser, who acted as the prosecuting attorney, said some of the photos were of Rajib Mitra’s then-underage girlfriend engaging in sexual conduct.

Mitra pleaded not guilty to the charges, claiming he did not take the pictures of his girlfriend and claimed he had never seen the child pornography on his computer, Kaiser said.

Kaiser said Detective Cynthia Murphy of the Madison Police Department was able to obtain those photos and other encrypted child pornography in 2009 after years of trying to break through the encryption.

Mitra, 32, was a UW graduate student in 2003 when he scrambled police radio waves during Halloween weekend, an act for which he was later found guilty in a 2004 federal trial.

Mitra was first arrested in Nov. 2003 when Madison police traced radio interference back to his apartment. He had been broadcasting audio pornography on police radio channels during the State Street Halloween celebration, which ended that year with police tear gassing partygoers who had started to riot.

During the federal trial, Madison police officers said Mitra’s radio interference hurt their ability to control the riots.

He was found guilty of intentionally blocking police radio communications, but the investigation into his files continued when computer and radio experts searched his computer to find files they suspected to be child pornography.

Murphy, who had a background in computers as well as child pornography cases, recognized some of the file names in Mitra’s computer and suspected they contained illegal images, Kaiser said.

Kaiser said Mitra’s computer skills and encrypting abilities greatly exceeded those of a normal person’s.

“Mitra had an enormous store of computer expertise,” Kaiser said.

During the time Murphy was searching his computer, Mitra sued her to get it back, Kaiser said.

Mitra is currently being held in a federal prison in Sandstone, Minn., for the crimes he committed in 2003, and will be released from his federal sentence next month, Kaiser said. He is expected to be sentenced for the child pornography charges later this year.