An opposition MLA wants Alberta Attorney General Verlyn Olson to call an independent review into the prosecution of an assault case involving an RCMP officer.

"Right now, saying 'Trust us. The decision came out the way we think it should have. Don't worry. Go on about your business.' That's not good enough," NDP justice critic Rachel Notley said.

Earlier this week, Alberta Justice declined to explain what happened in the prosecution of RCMP Const. Shawn Kropielniski in the November 2009 assault on Eric Oullette, who was then in custody at the Bonnyville detachment.

A CBC News investigation revealed that a video showing Kropielniski assaulting Oullette was not shown at a hearing in Fort Saskatchewan provincial court on May 13.

According to a court transcript, Crown prosecutor Kevin Fotty told Judge Marilyn White he could not get the DVD to play.

Instead, he described the assault to the judge but didn't mention that the video shows Kropielniski giving Oullette two elbow strikes to his head while another officer had Oullette in a chokehold.

Kropielniski pleaded guilty to the assault. The judge accepted a joint submission from the Crown and defence and gave Kropielniski a one-year suspended sentence.

Assistant deputy minister Greg Lepp is in charge of Crown prosecutors in Alberta. Lepp reviewed the prosecution of the case and he concluded justice was done.

Assistant deputy minister Greg Lepp is in charge of Crown prosecutors in Alberta. CBC"Given that the Crown expected to play the video, the video wouldn't play, and then the Crown was in the position on his feet to recount his recollection of the events — I conducted my analysis," Lepp said. "I'm absolutely convinced ... that this was an innocent issue and it was not a deliberate attempt to mislead the court at all."

Lepp said the system worked properly in this case.

"There was an allegation of assault against a police officer," he said. "It was investigated by the police. It was prosecuted by the prosecution service. It came to court. The appropriate charge was laid. A conviction was entered and an appropriate sentence was passed."

But lawyer D'Arcy Depoe from the Criminal Trial Lawyers' Association disagrees with Lepp's assessment. He says it is up to the judge to decide whether a sentence is appropriate or not.

"It's difficult to say there was a just outcome because the judge was not presented with the proper facts as shown on the video," he said.

Fotty resigned last week but Alberta Justice said his decision to step down had nothing to do with the Kropielniski case.

With files from the CBC's Charles Rusnell