Garry Prokopishin sat emotionless in a Calgary courtroom today as one of his former foster sons testified he was repeatedly molested over the four years he lived in Prokopishin's home.

Garry Prokopishin, a former foster parent, faces several sex-related charges. (CBC)

Prokopishin, 51, faces six charges of sexual exploitation. He has pleaded not guilty to all charges.

The alleged incidents are believed to have happened between December 2004 and June 2008. 

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Garry Prokopishin, a former foster parent, faces several sex-related charges. (CBC)

The trial is set to last six days and five other former foster sons are expected to testify during the proceeding.

The first allegation came to light in 2009 and more boys who lived in the home as teens came forward with similar allegations of abuse in the following years.

The man who testified today is now 26, but was a teenager at the time of the alleged crimes. His identity is protected by a publication ban.

In his testimony, the alleged victim told the judge Prokopishin would perform oral sex on him weekly — paying him $20 after each incident.

The witness also said Prokopishin would take the boys on out-of-town trips with sexual contact expected in exchange.

Investigation continues

But he said it was an opportunity he never would have had otherwise.

"I wanted to go. I wanted the extra perks: clothing, dinner, liquor, a night in a hotel, the type of stuff you wouldn't get as a kid living on the street," he told the court.

The witness said he was embarrassed to say anything, and didn’t think his complaint would be taken seriously.

"I didn't think anyone would believe me. They were foster parents of the year, we're street kids," he said.

In cross-examination this afternoon, Prokopishin's lawyer suggested the witness was lying and there was no time or opportunity for the acts to take place.

Fifty-five foster children, all boys between the ages of 14 and 17, have lived under Prokopishin and his wife's care in the past 20 years, police said. Between four and five teenage boys lived in the home at any given time.

The investigation is continuing and interviews are being conducted across Canada, officials said.

Prokopishin's foster home was suspended in June 2009 when the investigation was launched. There are no children in the home now.

The Alberta Foster Parent Association named Prokopishin one of the foster parents of the year for 2006. Prokopishin also served as a director of the Calgary and District Foster Parent Association.

With files from Meghan Grant/CBC