The lawyer for a military reservist says his client's conviction in a fatal training accident in Afghanistan is totally unreasonable.

Balfour Der told a court martial Friday that Lieut. Darryl Watts of Calgary was put in an untenable position when he was placed in charge of the training range in February 2010. 

Cpl. Josh Baker was killed and four other soldiers were injured when a C-19 Claymore anti-personnel mine misfired.

Watts was found guilty in December 2012 of unlawfully causing bodily harm and negligent performance of military duty. He was demoted two ranks to lieutenant from major and given a severe reprimand.

Der said Watts made it clear he was untrained on the C-19 and shouldn't be held responsible. Watts is appealing both his sentence and conviction.

His lawyer argued that Watts should be acquitted or at least granted a new trial.

The conviction and sentence appeal arguments were heard by a panel of civilian judges today. They have the option of acquitting Watts, ordering a new trial, changing his sentence or upholding the original conviction and sentence.

A date for a decision has not been set.

Cross-appeal filed

The prosecution has filed a cross-appeal, but Der said before the hearing that he wasn't concerned.

"The prosecution have cross-appealed the sentence only. There is always a risk the sentence could go up, but I believe, if anything, the sentence would go down."

Baker, 24, died when the anti-personnel mine loaded with 700 steel balls peppered his platoon on the practice range. Four other soldiers were hurt when they were hit by the blast.

The prosecution argued during his trial that Watts, who was the platoon commander, didn't enforce safety standards and abdicated his duty as leader when he handed over responsibility for range safety to Warrant Officer Paul Ravensdale.

Watts argued that he had never been trained on the C-19 and as a result was not qualified to be in charge.

Military prosecutor Maj. Anthony Tamburro has said his position on the case remains unchanged.

'This case is important'

"The Crown takes the position that commanders remain accountable for the manner in which delegated tasks are carried out by their subordinates," Tamburro told The Canadian Press.

"This case is important as the decision of the Court Martial Appeal Court will help to define what being in command means in the Canadian Armed Forces."

The day of the accident the range was divided into four training sections. The first two tests of the anti-personnel mine went off without a hitch.

But during the next one, the ball bearings fired backwards, hitting Baker and the others.

Videos show several soldiers, including Watts, standing around and watching the test. They are not inside armoured vehicles or standing behind them for cover, as set out in military safety regulations.

Two other soldiers have also been convicted for their roles that day.

2 other soldiers convicted

Christopher Lunney pleaded guilty Sept. 13, 2012, to negligent performance of duty for failing to ensure Watts was properly qualified on the C-19.

He said he had assumed that to be the case because of Watts's rank. Lunney was demoted one rank to captain from major and received a severe reprimand.

Ravensdale, who was running the exercise that day, was found guilty last year of breach of duty causing death, breach of duty causing bodily harm, unlawfully causing bodily harm and negligent performance of military duty. He, too, was acquitted of manslaughter.

The now-retired soldier was given a six-month suspended sentence. He also received a fine and was demoted one rank to sergeant.

Der said his client believes the appeal is the right thing to do.

"Darryl is holding up well but looking forward to having the appeal heard. He is cognizant of the implications to him personally, but also cognizant of the legal significance this case has to the law of negligence for all soldiers," Der said.

With files from CBC News