A new trial has been ordered for a man convicted of first-degree murder after Ontario's highest court found that some recently implemented changes to the jury selection process should not have applied to his case.

Today's ruling by the Court of Appeal for Ontario could affect several other criminal cases that have unfolded since the changes included in the sweeping legal reforms of Bill C-75 took effect last September.

The appeal was launched by Pardeep Singh Chouhan, whose first-degree murder trial had reached the jury selection phase on the same day the changes laid out in the legislation came into force.

Chouhan's lawyers said the new rules, which include scrapping "peremptory challenges" — a mechanism that allowed lawyers for either side to dismiss a certain number of prospective jurors without explanation — infringed on his right to a fair trial.

His lawyers also argued the changes should not apply to those who, like Chouhan, had already requested a jury trial before the new rules took effect, even if the trial itself began after that date.

In a unanimous decision released today, the appeal court said the elimination of peremptory challenges did not infringe on Chouhan's rights, but that given the timing, the change should not have been applied to his trial.