Singh, 48, had five hours sleep in the three days before the crash and spent much of that time dealing drugs and using them with associates. Prosecutors say the combination of fatigue and his use of the drug ice impaired his ability to drive.
On Friday, defence counsel Peter Morrissey, SC, said Singh accepted he chose to drive that day, but was prepared to give evidence against Mr Tuteru, who police allege knew the truck driver shouldnt have been working.
Senior Constable Kevin King, Constable Josh Prestney, Leading Senior Constable Lynette Taylor and Constable Glen Humphris were killed on the Eastern Freeway.
Mr Tuteru is charged with four counts of manslaughter and is due to face court in May. His lawyer has said he would fight the charges.
In a text message exchange on the morning of April 22, Singh raised concerns he was not fit to drive with Mr Tuteru, and the two men spoke at the Lyndhurst depot that afternoon. Other staff at Connect Logistics had previously raised concerns over Singhs fitness to drive.
Mr Morrissey said the truck driver faced sustained pressure to drive from Mr Tuteru, was vulnerable to influence given his mental state and personality type and was concerned at being sacked as he was on a six-month probation with the company.
The boss leaned on him to drive but true it is, he [Singh] didnt disclose he was on drugs, Mr Morrissey said.
Justice Paul Coghlan questioned whether Mr Tuteru knew of Singhs drug use, and said although he understood there was pressure applied, the crash happened at the start of Singhs shift.
The boss who encouraged him to drive did so with one hand tied behind his back, Justice Coghlan said.
The judge asked if Singh was blaming someone else for his crimes. Mr Morrissey said he didnt want to direct guilt towards Mr Tuteru.
Mr Morrissey said his client who has pleaded guilty to four counts of culpable driving causing death, three of drug trafficking and other charges was ultimately the one responsible for the officers deaths.
Mohinder Singh enters the Supreme Court on Thursday.Credit:Jason South
He chose to drive, he said of Singh.
Singh used ice for five years, the court heard, and was also a believer in the supernatural who thought he was cursed by a witch named Glenys who wouldnt get out of his passenger seat.
Forensic psychiatrist Andrew Carroll said Singh feared he was more vulnerable to the witch if he slept.
He was intensely preoccupied that day with witches, curses, stick figures and the like, Dr Carroll said.
Richard Pusey.Credit:Nine News
But he said Singhs decision to drive was not directly driven by a delusion or a hallucination and although he was in a psychotic state, it was separate to an intoxication from ice.
Dr Carroll found Singh was impulsive in decision-making, lacked insight into his drug use, tended to adopt supernatural reasoning over rational explanations and had low confidence, which meant he didnt assert himself with his boss like others would.
But the psychiatrist said the truck driver knew he shouldnt drive if drug affected.
Mr Morrissey apologised on Singhs behalf to the officers families.
Singh, his barrister said, told investigators after the crash he felt sorry for the police and their families, and admitted he shouldnt have driven.
It was a big accident, he had told police.
They [the families] are probably waiting for them to come home. Imagine it was my kids or your kids. Oh God.
Mr Morrissey conceded Singhs drug use, lack of sleep, his knowledge he shouldnt have driven but did for a long distance Kew is 50 kilometres from Lyndhurst aggravated his crimes.
Chief crown prosecutor Brendan Kissane, QC, accepted Singh faced pressure from work to drive, but said it was his decision and the gravity of the crimes was high.
Mr Morrissey asked Justice Coghlan to consider Singhs early guilty plea, remorse and his hopeful rehabilitative prospects.
The father of two remains in custody and will be sentenced on April 14.
Pusey has pleaded guilty to outraging public decency and other charges for filming Leading Senior Constable Taylor while she was critically injured. He is in custody awaiting a plea hearing on March 31.
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Adam Cooper joined The Age in 2011 after a decade with AAP. Email or tweet Adam with your news tips.