A man accused of taking part in a Hells Angels hit in Dartmouth, N.S., has had his murder conviction overturned and a new trial ordered by Nova Scotia's highest court.

Steven Gerald Gareau, originally from Ottawa, was convicted of first-degree murder and conspiracy to commit murder for the October 2000 shooting death of Sean Simmons.

Simmons was gunned down in an apartment in north-end Dartmouth on orders from a Hells Angel because Simmons allegedly had an affair with a gang member's wife.

Gareau did not pull the trigger. He argued that he did not even know there was a plan to kill Simmons that day. Gareau told his trial that he was only meeting Simmons for a drug deal.

In a ruling released Wednesday, the Nova Scotia Court of Appeal overturned Gareau's conviction. It said the jury that found him guilty should not have heard testimony about another shooting, and his lawyer should have been able to cross-examine a witness on part of a recording he made with Gareau.

Dean Kelsie was the actual shooter. Evidence presented at trials showed Kelsie, Paul Derry, Tina Potts, Wayne James and Neil Smith planned the murder.

Derry and Potts reached an immunity deal with the Crown and avoided charges by agreeing to testify against the other conspirators.

In his testimony at Gareau's trial, Derry said Gareau had been present at an attempted murder that happened a few years before the Simmons killing.

Gareau's lawyer argued the testimony was highly prejudicial and had nothing to do with the murder charge. The court of appeal agreed the jury should not have heard about the earlier shooting.

In addition to testifying at the trials, Derry also allowed police to record conversations he had with the accused. Gareau's lawyer argued he should have been allowed to question Derry about one of those taped conversations.

In the conversation, Gareau said: "I wasn't aware of it."

Derry replies: "What's that?"

Gareau: "I wasn't aware."

Derry: "Exactly."

Gareau's lawyer said this exchange supports Gareau's argument that he didn't know about the murder plot against Simmons beforehand. The lawyer said he should have been able to cross-examine on the last part of the recording but the trial judge wouldn't allow it.

The appeal court said the trial judge was wrong to limit the cross-examination.

If the Crown proceeds, this would be Gareau's third trial on the murder charge. He was convicted in 2004, but that conviction was overturned on appeal.

Kelsie is also appealing his murder conviction. Earlier this month, the Nova Scotia Court of Appeal ruled the government should cover the cost of a lawyer for his appeal.