Retired warrant officer Paul Ravensdale faces six charges, including manslaughter, unlawfully causing bodily harm, breach of duty and negligence, stemming from a training exercise in Afghanistan that turned fatal.
In February 2010, a platoon was testing anti-personnel mines in Afghanistan when one mine misfired and shot steel balls backwards toward the soldiers.
Cpl. Josh Baker died and four soldiers were injured.
Ravensdale was in charge of that exercise. It is alleged that he violated a number of safety procedures before the fatal explosion by letting other soldiers stand too close to the mine without being in a dugout or under cover.
But Ravensdale's lawyer, Maj. Philippe-Luc Boutin, said Ravensdale told his platoon members to stand behind vehicles.
Boutin also said Ravensdale's training plans were ordered and approved by his superiors, and he was bound by them.
Boutin said the weapon misfired — something no one could foresee.
Closing arguments in the court martial wrapped up on Monday. The five-member military panel could start its deliberations as early as Tuesday.
Two other soldiers have already been convicted in the accident.
Maj. Christopher Lunney has been demoted to captain and given a severe reprimand after pleading guilty to negligent performance of duty in connection with the incident.
Maj. Darryl Watts is awaiting sentencing on charges of negligence and unlawfully causing bodily harm.