A man who killed a colleague in a frenzied knife attack is suffering from a paranoid personality disorder, a jury has been told.

Two consultant psychiatrists called by David Squelch’s defence both agreed that when Squelch attacked James Wallington he was unable to make a rational judgement nor exercise self control because of his mental impairment caused by the disorder.

Dr Michael Bott, one of three psychiatrists who interviewed Squelch, told Canterbury Crown Court that he did not know what had gone on in Squelch’s head moments before the attack in March at Cory Environmental Recycling Centre in Tunbridge Wells.

“What I think happened is that the accumulation of all the perceived insults and belittling comments reached an explosive point and he was no longer able to contain it,” Dr Bott said.

“If Squelch had been a normal person and subject to these taunts and insults he might have just shrugged it off. To us they may seem irritating but to him they were overwhelming.”

Squelch, who has denied murder but admitted manslaughter due to diminished responsibility, lived with his father. His mother died in February, 2014.

Dr Bott said Squelch bore grudges against people whom he felt had belittled him going back many years. “He does not forgive and forget,” he added.

Squelch, 48, of Maidstone Road, Paddock Wood, had told him he suffered a blackout and he ascribed this to what Mr Wallington had been saying and doing.

This was when he started carrying a hunting knife with him in his bag.

Dr Bott said a week before the stabbing was the anniversary of the death of Squelch’s mother.

Mr Wallington made a comment to Squelch about a mother’s day card which angered Squelch and he was still angry about this when he stabbed Mr Wallington.

“Squelch told me that Mr Wallington had hurt him emotionally,” Dr Bott said.

“His paranoid personality disorder meant he could not make a rational judgement.

"What he did was irrational but his disorder had totally impaired his ability to exercise self control.

"In my opinion this disorder explains his stabbing of Mr Wallington. I can think of no other explanation for his behaviour.”

Dr Norman Lockhart also said Squelch, whom he saw in September, had a paranoid personality disorder and a showed a pattern of misconceptions of what were quite innocent things on Mr Wallington’s part.

“Squelch misinterpreted lots of what Mr Wallington did, such as turning up the radio in the cab and leaving cans lying around,” Dr Lockhart said.

His accumulated rage at what Mr Wallington said or did and his disorder resulted in the stabbing, he added.

“In my opinion Squelch’s paranoid personality disorder is the complete explanation for what happened,” Dr Lockhart said. “The fact that he managed to maintain control for substantial periods of his life does not alter the diagnosis.

“Squelch managed his rancour towards Mr Wallington and on the surface they got on.

Someone with this disorder can manage some form of normality while feeling angry inside.”

Mr Wallington, 44, of Somerset Road, Tunbridge Wells, received 17 wounds and died less than an hour later.

The trial continues.