A Saskatoon man who faces jail time over a collection of child pornography police found on his home computer says he downloaded and viewed more than two dozen graphic videos of sexual abuse against prepubescent kids several times as "research" for the "somewhat auto-biographical" novel he was writing four years ago.

"I didn't feel like I was doing anything wrong because my intent was not to use this stuff in any evil, wrong or immoral way," Michael Jeffery testified during his trial in provincial court Thursday.

The 63-year-old was charged in November 2007 with possessing child porn and making it available to others after city police executed a search warrant at the apartment he shared with his adult son, Aaron.

Aaron Jeffery was initially arrested as a suspect in the case. He spent a harrowing day in custody while investigators questioned him, and was then cleared of suspicion - although his father continued to deny all knowledge of the illegal material.

Aaron Jeffery died of a cocaine overdose last year, court heard. At the time of his death he was still living with his father, who was awaiting trial.

On the witness stand Thursday, Michael Jeffery admitted he lied to the police on the day of the search warrant, when he claimed to know nothing about the horrifying pictures and videos on his computer, which was set up in their living room.

A veteran Internet child exploitation unit investigator obtained the warrant after finding a list of known child porn files in the public "shared" folder of a Limewire account associated with the computer, the trial has heard.

Limewire is one of many Internet-based file-sharing programs that allow users to download music, videos and other material free of charge from fellow users around the world - including illegal files such as child porn.

Unless a user makes certain changes to the software's default settings, copies of all downloaded files are added to that user's "shared" folder, which makes them accessible to everyone else on the network.

"I didn't understand the word 'file sharing,'" Jeffery testified, telling court he thought it was a one-way transaction in which he got what he was looking for, without offering anything in return.

"I thought Limewire was just another search engine - with the difference that apparently the more well-known websites have policies against uploading illegal material," he said.

A draft of Jeffery's lengthy three-part novel was filed as a defence exhibit at his trial. It contains no reference to child porn, court heard.

Jeffery said he'd been suffering from "writer's block" for several months in 2007 and was unsure how to end the novel until he came up with the idea of having its main character become obsessed with child porn, then getting caught by his son and having his life ruined before finally finding redemption.

Judge Doug Agnew has reserved his decision on the case until Jan. 5.

StopPedophilia.com update - Sentenced in February 2012 to 14 months, plus 3 years probation for child porn distribution