“I would certainly expect to see a more serious escalation before the outcome that we saw in this case,” she said.

A recent four-year study,showing men who killed their past or current partner almost invariably had long histories of violence,seemed to back Mallett’s analysis. In thewords of the study’s lead author:“these are not men for whom violence comes out of the blue”.

Farquharson was taking anti-depressants after the breakup of his marriage and had,at times,contemplated suicide. But his counsellor gave evidence that,in the months before the fatal crash that he had been improving,and he was considering reducing his sessions.

Farquharson was convicted in 2007 and again in 2010 of triple murder afterhe drove into a dam on Father’s Day in 2005 with his three boys – Jai,10,Tyler,7,and Bailey,2 – in the car. Farquharson escaped but his sons didn’t.

The case against Farquharson is described as a “strands of the rope” case,and the final,and arguably most important strand,canvassed in this week’s episode ofTrial By Water,was his disturbing behaviour in the hours and days after the boys died.

One of his first actions after getting out of the dam where the car had sunk was to ask the young men who picked him up on the side of the highway to take him to see Gambino to tell her he’d killed the boys.

In the second trial,prosecutor Andrew Tinney told the jury that Farquharson had planned and executed his murder plot then demanded to be taken to see Gambino for the “delicious reward” of seeing the expression on her face when he told her the children were dead.

Farquharson also refused offers from people to dive into the dam to try to find the boys. He did not dive in himself. On the side of the dam,he repeatedly asked others for cigarettes.

In a police interview at Geelong hospital on the night the boys died,he said,“I gathered that” when told they were dead,and then asked at least twice:“What’s the scenario for me?” His demeanour made police immediately suspicious,and was partly responsible for the case being referred the following day to the homicide squad.

Throughout the investigation and two prosecutions,Farquharson did not provide details of what had happened in the dam. When he was asked,his evidence had gaps and was inconsistent.

Despite the importance of this demeanour evidence,and the prosecution’s argument about the motive,neither Tinney,who is now a judge,nor the prosecutor in the first trial,Jeremy Rapke,obtained a psychological or psychiatric report. Defence barrister Peter Morrissey likewise did not commission one.

Victoria Police has said it “stands behind the rigorous investigation”. The Office of Public Prosecutions and Morrissey both declined to comment about the case.

Mallett said the lack of a report was “weird”.

“I mean if they’re saying that this[murder] was because of psychological pressure ... then I would definitely expect a psych report,or probably one for the prosecution,one for the defence,” she said. “Surely if it hinges on his mental state,how have they not assessed his mental state?”

Criminal psychologist Tim Watson Munro agreed:“Given the magnitude,I mean,it’s a triple murder ... I find it extraordinary,” he toldTrial By Water.

Afterthe Hoddle Street massacre in 1987,when mass shooter Julian Knight killed seven people and injured 19 with a high-powered rifle,Watson-Munro said he had assessed Knight,as had a number of other forensic psychologists and psychiatrists,including the chief crown psychiatrist of Victoria.

Watson-Munro said these were not to test an insanity defence,but simply to try to explain why Knight had committed his crimes. “I’m staggered no psych report was tendered[in the Farquharson case],” he said.

Watson-Munro said the kind of report he was talking about would have included a comprehensive personality assessment and tests for disorders such as psychopathy.

In its absence,the only psychological evidence at Farquharson’s trial came from his Geelong-based counsellor and psychologist,Dr Peter Popko. In a three-page report and a police statement,Popko said Farquharson had been angry at the breakdown of his marriage to Gambino,but his anger “wasn’t extreme or threatening”,and he’d been “grateful that Cindy gave him open access to the kids”.

Farquharson was making “very good therapeutic progress” in counselling. “My personal opinion,” Popko told police,“is that it is highly unlikely that Rob would have done anything to hurt his kids.”

A prison psychologist who saw Farquharson in 2011,three years into his 33-year sentence,wrote in the prison medical records:“We are[either] dealing with a man who is innocent and wrongfully imprisoned or a man who is in denial.”

Trauma specialist and psychologist Dr Rob Gordon toldTrial By Water that his assessment of Farquharson’s behaviour after the crash was that he,“didn’t see a monster there. I saw a very disorganised man who was having a lot of trouble being coherent about his experience”.

If Farquharson had successfully murdered his children,Gordon said he might have been traumatised by that,but he expected it would present differently.

“It was like what was traumatic is,‘I’ve done this’. And I think that’s very different from what we see in Mr Farquharson’s case,which is,‘I really can’t grasp what’s happening,and I’m reverting to a very simple,self-centred,what’s going to happen to me next?’,” Gordon said.

The trauma of the event would also contribute to the difficulty of remember its details,Gordon said.

Farquharson’s sister Carmen Ross said her younger brother had grown up the youngest of four children in a traditional,lower income household.

“He was a prem baby. He had turned eyes,so had to have corrective surgery on the eyes as a young kid. Broke his leg,you know,a lot of little injuries like that. So in one way,he was behind the eight ball,” Ross said.

“He didn’t have any burning ambition ... Really didn’t care whether he was a brickie or a waiter or poured petrol.”

When Gambino had asked him to leave the marital home,Farquharson was angry,she said,“but he was dealing with that”. “He’d go for walks. The fact he was going to counselling ... I just think he handled that breakup really well and very maturely.”