Inside the mind of cruel control freak-killer Paul Thijssen who savagely ... trends now

Paul Thijssen was a control freak who showed 'next level cruelty' when he brutally murdered private school water polo coach Lilie James, a leading criminal psychologist believes.

Tim Watson-Munro said the bloody killing inside the gym bathroom at exclusive St Andrew's Cathedral School in Sydney's CBD last week was typical of 'fragile ego' men who become enraged by rejection and the end of a relationship.

He believes Thijssen, 24, snapped when Ms James, 21, jilted him after just five weeks and their brief affair was ended only days after he had boasted about it to students.

Thijssen then pre-planned her murder, arming himself with a hammer and arranging to meet for a final showdown at the school on Wednesday evening.

'He knew exactly what he was doing,' the renowned crime expert told Daily Mail Australia. 'These kind of guys are bad, they're not mad.

'This doesn't appear to have been a spontaneous act of violence. There's clear intention - if you take a weapon to a meeting, you may use it.'  

After Thijssen, 24, killed Ms James, 21, he then used her own phone to text her father, posing as the young woman asking for her dad to collect her from the school. 

'That's next level cruelty,' said Mr Watson-Munro, who has been an expert witness in criminal cases, including Melbourne gangster Alphonse Gangitano, to establish if the accused was legally insane.

'That's the ultimate control and humiliation of her and her family, and traumatisation of her family.

'This guy just sounds like a complete psychopath to me.

'It's not just killing her, but then cogitating and ruminating about what you've done, and how you can then inflict additional damage on the family.

'Who knows what the dynamic was between this poor woman, her family and this guy, but it's very personal when you start doing that sort of thing.'

Thijssen then fled the school and drove to the clifftops in Vaucluse in Sydney's east where he alerted police and ditched the murder weapon in a nearby bin.

He then jumped or fell to his death from a cliff at Diamond Bay Reserve and his battered and bloated body was finally recovered on rocks below on Friday morning.

Mr Watson-Munro believes the delay between alerting police to the murder and his own death was another indication of Thijssen taunting authority.

'It's this sort of "catch me if you can" narcissism,' he said. 'He wants to have the final say on this, even beyond the grave in many ways, and leaving clues.

'It's not that uncommon - I've looked at a number of these cases.'

He said women are being killed by their former partners at an ever-increasing rate, with 56 women murdered by men around the country already this year.

'It used to be around one a week, but we're already far past that and it's only just November,' he said.

'People say, "Well, these guys are crazy." They're not. They know what they're doing. And it's often very violent and brutal.

'You look at the murder of Hannah Clarke who was the woman who was set alight in her car with the children [in Brisbane in 2020]. Same deal. 

'[Her estranged husband Rowan Baxter] knew what he was doing. He arrived with a gurney full of petrol.

'We need to do a lot more about this. It's happening with frightening regularity.'

While there is little police can do to prevent such acts, Mr Watson-Munro said women can be forewarned by red flags in their partner's behaviour. 

'Generally the most dangerous time for women in terms of potential homicide is when they decide to leave,' he said.

'But prior to that, there's been all this sort of behaviour occurring in escalating degrees of intensity.