A man who fantasised about killing almost all the time has been found guilty of the murder of a 21-year-old with learning difficulties.
Dean Shorney was described as having 'the mind of a child'
A Cardiff Crown Court jury took under 30 minutes to return their verdict on Wayne Royston who denied the charge.
The four-week trial heard he launched a "frenzied attack" on stranger Dean Shorney in Bargoed, Rhymney Valley.
Royston, 35, who lives locally and who has a dangerous, severe personality disorder, will be sentenced on Friday.
The trial was told Mr Shorney, a popular figure in the Bargoed community, suffered 38 stab wounds and had his throat cut from ear to ear by Royston.
The 21-year-old - described in court as "a harmless soul who would never hurt a fly" - had returned from a day out in Porthcawl last April when he was attacked in his local park.
Officers arrested Royston two days later and discovered an array of weapons including two samurai swords, a machete and an axe at his house.
They also found a pair of jeans at the bottom of a wash basket which had a bloodstain matching a sample of DNA from Mr Shorney.
"The chances of those stains coming from someone other than Dean Shorney are one in a billion," prosecution Peter Murphy QC told the court.
The prosecution also said unemployed father-of-one had had homicidal thoughts for several years with doctors first raised concerns with police in 2003.
A report by a psychiatric doctor that year showed he had admitted a number of incidents, including trying to suffocate an ex-girlfriend, having homicidal thoughts about a manager at work and a woman he had been having an affair with him.
Mr Shorney's body was found at a park in Bargoed
Doctors deemed him as having "high risk of severe violence, perhaps even of killing someone," and Gwent Police were informed.
Later Royston was diagnosed as suffering from dangerous severe personality disorder which was considered untreatable.
Two years later, the court heard, Royston told doctors he was "having homicidal thoughts all the time" and that a month before the murder, he said his thoughts about killing had worsened.
His medication was altered but on the day of the killing he had been unable to obtain a repeat prescription of sleeping tablets because of an administrative error.
Royston was also found guilty of a separate charge of attempting to pervert the course of justice for giving police a false alibi.
After the jury returned its verdict, Robert Shorney said he would never forgive his son's killer.
"I absolutely detest the man. I can't find the right words to describe him," said Mr Shorney.
"There's not a strong enough word for him."