Authorities knew the man who fatally stabbed Melbourne schoolgirl Masa Vukotic was refusing to take medication for years before allowing him to be released into the community, a court has heard.

Sean Christian Price, 31, has pleaded guilty to murdering Ms Vukotic in a park near her home in Doncaster in March.

Price, who has a history of mental illness and violent sexual offending, was under a supervision order when he committed the crime after being released from a specialist sex offenders unit in October 2014.

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The Supreme Court heard Price had refused to take medication for schizophrenia for up to four years.

Prosecutor Michelle Williams told the court authorities were aware Price was “non-compliant” with orders to take his medication when he was released into the community.

“Why did that happen if they knew he wouldn’t take his medication?” Justice Lex Lasry asked.

“I can’t particularly answer that question,” Ms Williams replied. “It’s alarming.”

Masa Vukotic, 17, was walking through a park near her home when she was murdered. Photo: AAP

The court also heard a psychiatrist who assessed Price determined his risk of reoffending would elevate quickly if he was not taking medication.

The court was told about a psychological report written after Price committed sexual offences in 2002 and 2005.

In it, he said: “I don’t think it was about sex, it was more about torture.”

The prosecution is seeking a sentence of life in prison without parole for Ms Vukotic’s murder.

Price is defending himself in court after he dramatically fired his legal team on Monday.

He told the court he did not deserve life without parole because he believed he could be rehabilitated.

“I don’t think it’s been proven … that I can’t be rehabilitated,” Price said.

Price admitted he refused to take medication for his schizophrenia and described the drugs as “torture”.

“I don’t like it … it hurts,” he told the court.

“Every expert has indicated there is something wrong with me up top.”

Price denied the prosecution’s claim that he had refused other forms of treatment.

Price told the court on Monday he accepted full responsibility for his actions.

“I want to apologise for my crime,” he told Justice Lasry.

“I don’t wish to make any excuses for my actions … I simply wish to take the full consequences.”

The court heard Ms Vukotic had 49 stab wounds to her chest, neck and body and was targeted at random.

The court heard Price had a history of violence, serving five-and-a-half years in a high-security mental health institution for a series of assaults and rapes in 2003.

Price will be sentenced at a date to be fixed.

–ABC