Karl Lilgert's lawyer asked the court to overturn convictions of criminal negligence causing the deaths of two passengers, who were never seen after the Queen of the North ferry sank in March 2006 and were presumed drowned.
A jury found Lilgert guilty last year and he was sentenced to four years in prison, though he was released on bail pending his appeal.
Lilgert was the navigating officer on the Queen of the North as it made an overnight voyage from Prince Rupert to Vancouver Island. The vessel missed a routine turn and struck an island.
His lawyer, Glen Orris, told a three-judge Appeal Court panel that the trial judge incorrectly defined the offence of criminal negligence causing death when she explained it to the jury.
In particular, Orris noted, the judge told the jury Lilgert had a duty to safely and properly navigate the ship in accordance with marine rules, known as collision regulations.
Orris said those regulations are merely guidelines, which leave navigators with a level of discretion. And while he acknowledged Lilgert had a legal duty to navigate the ship, he said that doesn't mean any mistakes that result in a collision are necessarily criminal.
"He had a legal duty to navigate, and obviously to navigate safely is the goal of all navigators, but it's not a legal duty," said Orris.
Lilgert was on the bridge with his ex-lover, quartermaster Karen Briker — their first time alone together since their affair ended several weeks earlier. The Crown alleged Lilgert did not take any meaningful steps to navigate the ship because he was distracted by Briker, either because the pair were arguing or possibly having sex, which Lilgert denied.
Lilgert testified he was doing the best he could to navigate the ferry through rough weather, though he couldn't explain why the ship rammed into an island.
Orris said the law surrounding criminal negligence causing death is complex, and the trial judge didn't take into account recent decisions from other courts, including the Supreme Court of Canada.
He said the judge told the jury to compare Lilgert's actions with what a reasonable person would have done in the circumstances. Orris said the standard should have been what a trained professional mariner would have done.
Orris also noted the judge told the jury not to consider what may have been in Lilgert's mind as the ferry sailed toward the island, but rather what he should have been thinking about.
He said the Supreme Court of Canada has said criminal negligence cases must take into account any explanations offered by the accused.
The result of the judge's instructions, Orris said, was that the jury was essentially told to disregard Lilgert's testimony that he was attempting to navigate the ship, whether or not they may have believed him.
Passengers Gerald Foisy and Shirley Rosette, a common-law couple from 108 Mile House, B.C., are believed to have gone down with the ship, though their bodies have never been recovered.
The sinking prompted both the Transportation Safety Board and BC Ferries to investigate and release reports on what happened. Both reports blamed human error and neither was shared with the jury.
The Transportation Safety Board report, released in 2008, concluded a "conversation of a personal nature" was among the factors that distracted Lilgert.
Lilgert and Briker both testified that there were no hard feelings between them and they each denied their relationship had anything to do with the sinking.
The Crown alleged Lilgert and Briker both lied.
Lilgert lives in Grand Forks, B.C., where he turned himself into the RCMP on Tuesday in accordance with his bail conditions, the court heard.
Orris asked that Lilgert's release be extended until the Appeal Court makes a decision, which the court granted.
Follow @ByJamesKeller on Twitter