TORONTO - A war deserter from the U.S. who fled to Canada was visibly tense Wednesday as he made his case for asylum for a second time, arguing he will face unfair prosecution if sent back to the United States.

Joshua Key told an Immigration and Refugee Board hearing in Toronto that what he was being asked to do in Iraq was "immoral" and it made him question the war he once supported.

"To me it was morally wrong what I was doing to Iraqi civilians," Key told the board member hearing his case. "It very much plays on me, it still plays on me."

Last July, Canada's refugee board was ordered to take another look at Key's case after initially denying him asylum. The Federal Court found the board made mistakes in turning down Key's claim.

At the time, Justice Robert Barnes said military misconduct falling short of war crimes may still support a claim of refugee status. Barnes also said actions that degrade or humiliate combatants and non-combatants would also support a claim.

Key and his family fled to Canada in 2005 while on leave after serving in Iraq for eight months as a combat engineer.

On Wednesday, Key said he conducted more than 200 arbitrary raids on ordinary civilians. Soldiers forced men outside of their homes, cuffing them, hooding them and sometimes forcing them to undress, he said.

Roger Gould, tribunal officer for the Immigration and Refugee Board, asked Key why his superior wanted the soldiers to do this.

"To dehumanize," Key replied.

There was a rigid chain of command, which prevented him from bringing his concerns forward because soldiers were often told "quit complaining or be charged," Key said.

A defence of misconduct or unfair treatment against Iraqi civilians would be inadmissible in a military tribunal, said Key, who added that means he would have no defence if sent back to the U.S.

His decision to publish a book about his experience would further damage any chance of fairness, said Key, who cited other cases of severe punishments for war resisters who spoke to media.

The immigration board member who heard Key's case reserved his decision.

After the hearing, Key seemed relieved.

"I believe in what I did. I don't believe I did anything wrong. I believe sending me back to the United States and punishing me, that's wrong," he said.

Key said he wants to start a new life with his fiancee and new baby in Saskatchewan, where he currently lives.

If his bid to stay is accepted, he'll face yet another challenge.

His ex-wife and four children have returned to the United States and he's not sure when he'll be able to see them again.

"You're worried, you're stressed and you're hoping for the best," Key said.