Serial killer 'victim' of illness, court told

Victoria's worst serial killer says he deserves a decreased sentence for the murder of six people because he was labouring under a mental illness at the time.

Paul Steven Haigh, 54, says he was the "victim" of borderline personality disorder when he murdered six people, including a 10-year-old boy, in the 1970s.

Arguing why he should be given a minimum term on his sentence of life with no parole, Haigh said he was afflicted with a similar personality disorder to that suffered by Hoddle Street mass murderer Julian Knight, which resulted in him receiving a 27-year non-parole term.

Haigh said he also should have received mitigation for his illness, which was more severe than Knight's.

"Knight's anti-social behaviour is negligible when compared with my own," he told the Victorian Supreme Court in his closing submission on Thursday.

Haigh said something "pathologically abhorrent" was working within him at the time of the "regretted atrocities" but that doctors had since determined he was no longer labouring under the illness, which typically diminished with age.

"Being afflicted with borderline personality disorder provides me with mitigating circumstances, as I was afflicted with something I did not ask for, choose to have or bring on myself," he said.

"I laboured under a borderline personality disorder that I respectfully say should carry weight in the scales of justice.

"I shouldn't be punished as if I was a normal person at the time of my offences."

Haigh has spent more than 30 years in prison for the murders and was also convicted of killing sex offender Donald George Hatherley, whom he helped hang in a jail cell in 1991.

He will conclude his submission on Friday after being given more time by Justice David Beach.