In February 2010, an explosion killed 24-year-old Cpl. Joshua Baker and injured four other soldiers during a military training exercise in Afghanistan.
Reservist Darryl Watts testified he was neither trained nor qualified to lead the exercise.
Watts, who was a captain at the time, was the officer in charge on the day of the accident.
Tony Tamurro, theprosecutor from the Office of the Judge Advocate General, says Watts faces charges because of his alleged poor supervision that day.
He told the court Monday morning that he had met with superiors to plan the training, but at no point was told he would be the officer in charge of the exercise or platoon safety.
Watts says his second in command was responsible for safety that day when Claymore explosives (C19s) packed with 700 steel balls hit the Canadian Forces platoon.
He said he had never seen or used a C19 before that day, and had no idea anything went wrong until he heard a call for a medic after a blast.
But during cross-examination, prosecution tried to establish that Watts was in charge of the platoon and was expected to be on top of all safety rules in the training.
Proper procedure would have had the military personnel dug in or behind cover, but a video played earlier in court shows soldiers standing in plain sight as the C19s explode.
If convicted, Watts could be sentenced to prison time in the Canadian Force's detention barracks in Edmonton or in a regular correctional facility.
Lesser punishments can include dismissal from the military, a reduction in rank or a fine. Two other Canadian Forces personnel were charged following the accident.