TORONTO - The role that fetal alcohol spectrum disorder should play in deciding violent offender status for a man with a long rap sheet of sexual assaults -- including one against a seven-year-old cousin -- will be weighed by Ontario's top court Tuesday.

The man's condition, caused by his mother's drinking during pregnancy, went undiagnosed and untreated for decades and was among the reasons a trial judge refused to name him a dangerous offender, which would have seen him jailed indefinitely.

The tragic disorder will be pitted against the 33-year-old man's history of violent sexual assaults against relatives and prostitutes as Crown lawyers argue to overturn the trial judge's sentencing decision before the Ontario Court of Appeal.

Part of the Crown's appeal will be based on the testimony of experts who have said the man "obviously considers his needs first, while empathy for his victims is rudimentary at best."

Court has heard the man -- who cannot be named to protect the identities of his victims -- was born in Vancouver in 1976 to two chronically alcoholic parents and was sexually abused by his father for several years starting at the age of six or seven.

Fetal alcohol spectrum disorder is a neuro-psychiatric condition and attention disorder that has been associated with mental health issues, struggles with education and employment, inappropriate sexual behaviour and a high likelihood of falling into trouble with the law.

The man struggled to learn to read and write, was expelled from high school and joined a gang.

When he was 18 he brutally sexually assaulted his 31-year-old cousin after a night of drinking, and repeatedly hit her with a beer bottle, punched her in the face and threatened to kill her with a carving knife when she resisted.

"She told me to stop and I didn't, so I kept on hitting her and hitting her and forced her to have sex with me," he told police after he was arrested, according to court documents.

He was released from custody while awaiting trial but was arrested again months later after sexually assaulting his seven-year-old cousin while he was babysitting her.

He pleaded guilty to sexual assault in both cases and a pre-sentence report suggested he "knew in each instance that his behaviour was wrong but each offence was planned and purposeful."

His sentence of eight years was extended by another 18 months after being convicted of two assaults against female jail guards.

In November 2004, he was released from custody in Toronto with a warning to his parole office that he was "an untreated sex offender who has anger and violence management issues."

Within months he was arrested again after attacking and raping a prostitute and another former sex-trade worker within a span of about a week.

He admitted he'd carried a cord with him for six months before the attacks, in case he had an opportunity to choke and rape a woman.

He pleaded guilty to two counts of aggravated sexual assault and two counts of choking and was sentenced by Superior Court Justice Frances Kiteley to 10 years in custody, after time served was factored in.

Despite expert testimony that he was still a very high risk to reoffend and would likely mount another violent and sexual attack upon release, Kiteley did not declare him a dangerous offender, and instead gave him long-term offender status.

A long-term offender can face up to 10 years of supervision in the community after being released, while a dangerous offender can be jailed indefinitely until a parole review determines they've been rehabilitated.

Kiteley ruled that the man had shown some signs of improvement in jail.

In 2003, about a year before being released from prison for the attacks on his cousins, he agreed to take medication that reduced his sex drive and took it for about six months. But he stopped after complaining of weakness, fatigue and lethargy and because the drug was causing him to grow breasts.

Court heard he is willing to take the drug again since becoming aware of breast-reduction surgery and other medications that would also help treat his impulsive behaviours.

It was also suggested that his risk of reoffending would decrease because of "burn-out theory," evidence that suggests male production of testosterone decreases significantly starting at age 45 leading to lower sex drive.

And Kiteley said he would not receive any treatment if declared a dangerous offender, since limited Correctional Service Canada resources are dedicated to prisoners who have a release date set and virtually no attention is given to those sentenced indefinitely.

"There is evidence that (he) can be meaningfully treated within a definite period of time. There is evidence that the resources needed to supervise him in the community are available," she wrote in her decision.

Kiteley said she also considered Supreme Court precedents dictating that sentencing cases involving aboriginals must be approached differently. She noted that case law suggests a sentence must consider the factors that have led to aboriginals being over-represented in jails.