THE son of a retired solicitor killed by a mentally ill man after their cars were involved in a minor collision has told a court of his family's deep sense of loss.

Andrew Lock said in a victim impact statement that a "huge piece of our hearts" went the day his father, Donald Lock, was killed.

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He added that he would not wish the same suffering his family has endured to be inflicted on their "worst enemy".

Paranoid schizophrenic Matthew Daley, 35, knifed 79-year-old Mr Lock 39 times on the A24 at Findon, near Worthing, West Sussex, on July 16 last year.

Daley stabbed Mr Lock after his Toyota crashed into the back of Daley's Ford Fusion at about 16mph, causing minor damage to both cars.

Before the killing, Daley's family had "pleaded" with clinicians to section him as his mental health declined, his trial heard.

Days before the trial started, chiefs at Sussex Partnership NHS Foundation Trust apologised to his relatives for not doing more.

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In the family statement read at Daley's sentencing hearing at Lewes Crown Court, Andrew Lock told of his family's deep trauma.

He said: "It's the most overwhelming pain that you can ever imagine and it catches you by surprise continuously.

"You can be talking and laughing one minute, and crying the next. We would not wish what we have been through on our worst enemy."

Mr Lock would have turned 80 last week and a big party had been planned by his widow before he was killed, his son added.

His voice trembling with emotion, he said his father was enjoying his retirement, cycling and following Brighton and Hove Albion FC, before he died.

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He went on: "He was a real gentleman who loved life."

Following the verdict, an independent review of 10 killings involving patients known to the Trust was announced, including Daley's case.

In May, Daley, formerly of St Elmo Road, Worthing, was cleared of murder but convicted of manslaughter.

Mr Justice Singh will sentence Daley after 2.15pm.