OTTAWA -- Society failed the young Ottawa boy who endured being chained up, tortured and sexually abused at the hands of his father, a disgraced former RCMP officer, the victim's maternal aunt told a sentencing hearing Wednesday.

The man, who cannot be identified under a court order aimed at protecting the identity of his son, sat silently in the courtroom with his head bowed throughout much of the hearing's first full day.

But it was the welfare of the boy -- and the enduring scars he carries as a result of the ordeal -- that were the focus of attention during testimony.

"The internal, invisible damage will be with him forever," the woman said of her nephew as she read from a victim impact statement that assailed the justice system and medical professionals for allowing the abuse to persist,

"Individuals and institutions put in place to help him failed."

Later, forensic psychiatrist Dr. Helen Ward told the Ottawa courtroom that the ex-Mountie was suffering from depression and post-traumatic stress disorder, but chose not to seek treatment because he thought he knew what was right.

In November, the man was found guilty of aggravated assault, sexual assault causing bodily harm, forcible confinement and failing to provide the necessaries of life.

He was initially arrested in 2013 after the boy was found wandering in a neighbour's back yard in search of water.

Court heard the boy nearly starved to death during his captivity, which left him chained and shackled, often naked, in an unfinished basement.

Ward, who was testifying as a defence witness, said the former officer exhibited "chronic and severe PTSD" while he was undergoing a court-ordered psychiatric evaluation, although she said the symptoms "fluctuated over time."

He was "re-experiencing" behaviours he was subjected to as a child, including flashbacks, expressed hopelessness and at times denied his own actions, Ward testified.

The former officer, who was fired from his job in December after initially being suspended, testified during his trial how he was abused as a young boy, and how he experienced armed conflict while growing up in Lebanon.

Court also heard the man refer to his son as "the devil" as he described how he was concerned he'd grow up to be a sexual predator.

"I think there's a link between what (the officer) experienced (as a young boy) and how he perceived his son," Ward said of the officer Wednesday.

"(He) clearly had a distorted view of his son."

But the former counter-terrorism officer also could have sought treatment for his own psychological issues but didn't, she added, linking his behaviour to narcissism.

"I think he believed that he was right" despite what others were telling him, Ward told the court.

Dr. Bradley Booth, who was called to testify as a Crown psychiatrist, largely agreed with Ward's assessment, saying the former officer was "likely" under the influence of PTSD at the time he was abusing his son.

In fact, he told the court, signs of the disorder were evident in a psychiatric evaluation conducted by the RCMP prior to the man joining the police force in 2001.

Both doctors said they didn't believe the man was "psychotic" or suffering from any mental illness that would deem him not criminally responsible for his actions.

In convicting the man last year, Ontario Superior Court Justice Robert Maranger dismissed the PTSD defence, and warned the ex-Mountie he was looking at serious penitentiary time.

The former officer's wife, the boy's adoptive mother, was also found guilty of assault with a weapon and failing to provide the necessaries of life in November and was later handed a three-year sentence.

The boy was 11 when his parents were arrested in February 2013.

His aunt recalled the night when news reports first alerted the family to the boy's escape from his home in suburban west Ottawa.

"I remember feeling the dread," she said as she described how the former officer had for years denied the boy access to his biological maternal family.

The man sought and was granted full custody of the child when the boy's mother died in 2009, subsequently isolating him from his late wife's family.

"He can never get back the years that he lost," the aunt said, her voice shaking. "He was so tiny and vulnerable."

The hearing is expected to wrap up this week.