Mental illness rendered Scugog man not criminally responsible for mother’s stabbing death


Published December 6, 2022 at 4:08 pm

Thomas Henderson has been found to be not criminally responsible for stabbing his mother to death in their Scugog home due to mental illness.

The courts have decided that a Scugog man who stabbed his mother to death was not criminally responsible due to his mental illness.

Rita Prendergast, 57, was found dead in her Blackstock home in September 2015, having suffered numerous stab wounds. Her son Thomas Prendergast, then 25, was arrested shortly afterwards and charged with second-degree murder.

Thomas Prendergast pled not guilty in a judge-alone trial years later in 2022. During the trial, Crown prosecutors presented “overwhelming” evidence of Prendergast’s guilt, according to Justice J. Speyer’s Reasons for Judgement.

Forensic pathologist Dr. Noel McAuliffe testified that Rita Prendergast had suffered more than 120 cuts, scrapes and stab wounds. Four stab wounds to her chest were found to have been the most significant, having damaged several internal organs.

Speyer found only Thomas Prendergast could have killed his mother. Only three people lived in the home at the time: Thomas, Rita and the patriarch, Gerald Prendergast. Gerald left the house before 7 a.m. on the morning of Rita’s death.

Three neighbours testified throughout the trial. The first said she had left her home around 11:10 a.m. and heard screaming as she made her way to an appointment. She heard a woman cry for help and a “very angry” man’s voice responded.

A second neighbour was in her garage when the “horrific” screaming started. She connected with the first witness, who then went back home to call 911. Durham Regional Police dispatched officers around 11:20. a.m.

The third neighbour was in her driveway talking around this time, admiring the landscaping of the Prendergast home when the door opened abruptly. Thomas burst out of the house shirtless and hopped into his mother’s car.

He quickly spun the car around with a three-point turn and backed the car up against the patio. He then opened the trunk, briefly rummaged around then went back inside, leaving the door ajar.

Shortly after he went inside, police arrived at the house. They immediately arrested Thomas, who had blood on his hands, arms and pants. They found Rita lying in the stairwell in a pool of blood

She had no pulse when police found her and the officers started CPR. Paramedics arrived to take Rita to hospital where she was pronounced dead.

Police raided the Prendergast home shortly after finding a bag of bloodied clothes and a large kitchen knife in the sink. The knife appeared clean, but DNA, most likely belonging to Rita, was found on the cutting edge.

Speyer found that the only logical conclusion based on the evidence was that Thomas had killed his mother. However, the Crown also sought to prove that Thomas was not criminally responsible for the killing due to mental illness.

This ruling works on the principle that an offender can not be liable for their actions if a mental disorder renders them unable to comprehend the “nature and quality of his act or of knowing that it was wrong.”

Ontario Shores forensic psychiatrist Dr. Jennifer Pytyck reported on Thomas’ state of mind. She found he most likely suffers from a treatment-resistant form of schizophrenia. This condition, a form of psychosis, often leads to hallucinations, delusions and disorganized thoughts.

Thomas demonstrated these symptoms for years leading up to his mother’s death and has suffered with them in the years since his arrest.

According to Pytyck’s report, Thomas led a happy, supportive life as a child. He played sports and had many friends. However, around age 17, he began to withdraw. He lost many friends, and suffered mood swings and behavioural issues.

In 2012, at age 22, he was hospitalized in Oshawa after threatening self-harm. The following year he was hospitalized twice more, the last time after crashing his car on the insistence of hallucinated voices.

Thomas received care from Oshawa’s Early Psychosis Intervention Outpatient Clinic throughout the summer, from May 2014 until September 15, 2015. He killed his mother nine days later.

Hallucinations continued to affect Thomas throughout treatment, and in August 2015, his psychiatrist switched his medication. Rita reported the switch was not going well but was told the new medication would take time to work.

Following his arrest, Thomas’ condition continued to deteriorate. He was moved from jail to hospital “as he had become increasingly delusional, aggressive and uncooperative.”

After returning to jail, Thomas was moved again to Ontario Shores. He was found unfit to stand trial and has remained at the facility since January 2016.

When Pyktyk interviewed Thomas, he was “pleasant, polite and cooperative” while obviously still suffering symptoms. Pyktyk testified that Thomas was aware of the legal consequences after stabbing his mother and tried to destroy the evidence and take her body out of the house.

However, she also found he “believed that he was killing a clone of his mother and therefore did not understand that his actions would cause his real mother’s death. He did not believe that the clone he was killing was a real person. He explained his beliefs about clones to Dr. Pytyck and told her that clones were made by a machine and did not have a soul.”

This belief in clones is known as a Capgras delusion, essentially the belief that a loved one has been replaced by an imposter. It is a rare, poorly understood condition and treatment options are limited.

As a result, Speyer found, “He knew that he was stabbing something, he knew that his actions would kill the thing he was stabbing, and he knew that he could be arrested for what he did and go to jail.”

“But the delusions from which he suffered rendered him incapable of appreciating that he was stabbing a real person who would die as a result of his actions. He was deprived, by his disease of the mind, of the mental capacity to foresee the physical consequences of his acts.”

Ultimately, Speyer felt this rendered Thomas incapable of criminal responsibility.


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