Stephanie Rengel was stabbed to death on New Year's Day 2008. (Toronto Police Service)

A 19-year-old man convicted of murdering teenager Stefanie Rengel at the urging of his girlfriend will probably commit a violent crime in the next 10 years but is unlikely to kill again, a psychiatrist told a Toronto court Wednesday.

Dr. Lisa Ramshaw diagnosed the man as having antisocial personality disorder and testified he had a history of violence ever since he was a child. He can only be identified as D.B. because he was 17 when he committed the crime, just four days shy of his 18th birthday.

Rengel, 14, was lured outside her Toronto home on Jan. 1, 2008, stabbed six times and left to die in a snowbank.

A risk assessment Ramshaw conducted on D.B. found he had a 58 per cent likelihood of violently reoffending within 10 years. She also found he is of average intelligence.

But Ramshaw said he is unlikely to commit murder in the future, saying Rengel's killing was the result of a unique set of circumstances.

Ramshaw told the court that D.B. was easily manipulated by his girlfriend, Melisssa Todorovic, who pressured him into killing Rengel out of jealousy.

Her report concluded he is emotionally immature and impulsive, and his obsession with Todorovic was so extreme he was willing to do anything to satisfy her.

D.B. can express remorse and has a capacity for empathy, she said. That finding is in contrast to psychiatric assessments of Todorovic, which found her to be lacking in empathy, self-pitying and with a capacity for manipulation.

'Did she scream in pain?'

When led into the courtroom Wednesday, D.B. looked solemn. He was wearing handcuffs.

He wept in court when Rengel's mother asked him if her daughter had begged for mercy.

"I lie awake at night wondering if he spoke to her before he plunged in a knife over and over," said Patricia Hung, Rengel's mother.

Hung asked D.B. if her daughter begged him to stop. "Did she scream in pain?"

D.B. wept as he heard Hung say there is no excuse for the cold-blooded murder he committed to secure a sex life.

Hung told the court that because the family knew D.B. before the crime, it was even more difficult to accept what he did to Stefanie.

Rengel's brother, 13-year-old Ian, said he wondered how D.B. could "be so messed up that he would take the life of an innocent person just because a girl told him so."

"Why would you take one of the most important people in my life away?"

Girlfriend sentenced as adult

In April, D.B. pleaded guilty to first-degree murder and admitted in court that he had killed the 14-year-old after being pressured and sexually manipulated by Todorovic.

Todorovic was sentenced as an adult in July to life with no chance of parole for seven years, the maximum for someone under 16 at the time of the offence, after being convicted in a separate trial of first-degree murder.

Todorovic was 15 when she used sexual blackmail via text messages and MSN chats to pressure D.B. into murdering her perceived rival — a girl she had never met.

The hearing now underway for D.B. will determine whether he will also be sentenced as an adult. If that happens, he could face a life sentence with no eligibility for parole for 10 years.

With files from The Canadian Press