Cpl. Stuart Langridge's mother told a Military Police Complaints Commission hearing that portions of her interviews with military investigators appear to be missing from audio recordings.
Sheila Fynes' allegations came as she was questioned over her dealings with the military and what she was told by them in the months after her son's death.
Lawyers suggested some of her interactions with them weren't reflected in transcripts of interviews, but she says the tapes appear to have been altered.
One of the portions missing was part of an interview with the military about where the soldier had been living in the days immediately before he killed himself in March 2008, Fynes told the hearing.
She said when she received the tapes via an Access to Information Act request, that section was gone.
When pressed later by the government's legal team as to whether the conversation had ever taken place, Fynes said she'd "go to her grave and bet her kids" that it had.
Also missing was a disparaging reference made about the officer assigned to help the family after Langridge's death and who had gone to bat for them with his superiors, Fynes said.
A lawyer for the government asked Fynes whether she believed the military's National Investigation Service had modified or destroyed the tapes.
"I don't know who modified them," Fynes said.
"But I know it's their recording."
The commission chair has ordered that the tapes be examined for signs of tampering though it set no deadline for that to happen.
The hearing into Langridge's death was called because of complaints by the Fynes family that the military's investigations were biased and focused on exonerating the Forces.
Langridge was a 28-year-old corporal and a veteran of both Bosnia and Afghanistan.
He'd been struggling with drug and alcohol addiction when he hanged himself in the Edmonton barracks.
His family also believes he was struggling with post traumatic stress disorder.
Fynes has told the hearing that her son received very little medical care in the months before his death, though doctors have testified they did all they could.
The military suggests that Langridge's suicide was linked to his drug and alcohol problems, not PTSD.
Government lawyers said Monday that Fynes didn't know the depth of her son's problems, saying that he'd told doctors he'd been drinking and doing drugs since he was a teen.
But Fynes said her son made a lot of things up if he believed it would get him help.
The hearing is examining both what happened in the days leading up to Langridge's death but also what happened afterwards.
Among the family's complaints is the fact that it took the family 14 months to receive a copy of her son's suicide note.
The family was told it was withheld because it was part of the investigation.
But it was obvious, Fynes said, that her son had killed himself. There was no reason to investigate any other cause of death, she said.
"The suicide note was our note," she said.
"There was no reason whatsoever for that note to be seized."
Under questioning from her own lawyer, Fynes said one of the two images that stick in her mind of her son's final hours is him sitting down to write the note.
"I just thought what a horribly lonely place he was in when he wrote that note," she said.
"And nobody even cared enough that we might want to see it."
The note had specified that Langridge only wanted a simple service, yet he ended up being given a full military funeral.
Fynes said family members were treated as "second-class citizens" at the funeral.
But government lawyer Elizabeth Richards suggested Fynes had a great deal of input.
Fynes helped pick the padre, the hymns, the casket and where her son was ultimately buried, said Richards.
"Most of what you asked for was respected," Richards said.
Fynes responded that it all had to be approved by her son's ex-girlfriend and they didn't have any decision-making powers over the event.
Langridge's ex-girlfriend is scheduled to testify later this week.
Commission chair Glenn Stannard expressed his sympathies to Fynes as she concluded her testimony.
The loss of a child is incredibly traumatic, Stannard said.
"Unless somebody has been through that, you really probably can't share that pain and I can't do that," he said.
"But I can understand the pain that you would go through."