The defence is calling for a mistrial in the case of two Regina men who've been convicted of manslaughter.

A sentencing hearing was set to begin Tuesday for Ashton Lavallee and Ronald Zerr. The pair were found guilty of manslaughter in the 2008 stabbing death of Albert Lowenberger.

Instead of discussing sentences, the defence applied for a mistrial, arguing the judge didn't properly instruct the jury and should have told them that not guilty of manslaughter was an option.

During trial, court heard that the stabbing happened in an altercation between two groups of people outside a Regina bar – the King's Head Tavern.

The trial heard two different versions of events, with some witnesses saying that Lowenberger was the victim of an unprovoked attack and the two men testifying they were defending themselves.

Court heard it was Zerr who fatally stabbed Lowenberger in the heart.

The defence said Tuesday the judge should have told the jury that if they accepted it was self-defence, they could acquit. 

In addition to manslaughter, Lavallee and Zerr were found guilty of one count of aggravated assault against Lowenberger's twin brother Robert, but not guilty of aggravated assault against the third man involved in the fight.

The Crown said last week it would seek a sentence in excess of 12 years. At that time, before the possibility of a mistrial was raised, one of the defence lawyers said eight years would be more appropriate.

Defence lawyer Bob Hrycan said only a new trial can fix the problem, as he sees it, with the instructions to the jury.

The matter has been adjourned for a few days to give the Crown prosecutor a chance to respond to the application for a mistrial.

The Crown's position will be heard on Thursday.