A man who stabbed to death a 21-year-old with learning difficulties in a "frenzied attack" in a park has been jailed for life.
Wayne Royston's wife had initially lied and given him an alibi
Wayne Royston, 35, was told he must serve at least 20 years for killing "harmless soul" Dean Shorney in Bargoed, Rhymney Valley, in April.
Judge John Griffiths QC, sentencing at Cardiff Crown Court, described Royston as manipulative, selfish and demanding.
Royston had denied murder but was found guilty by the jury in under 30 minutes.
Judge Griffiths said Royston "remained a very dangerous man".
A four-week trial had heard how Royston, from Bargoed, had a dangerous personality disorder and fantasised almost all the time about killing someone.
Mr Shorney, a popular figure in the Bargoed community, suffered 38 stab wounds and had his throat cut from ear-to-ear by Royston.
Dean Shorney was described as having "the mind of a child"
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 the unemployed father-of-one had had homicidal thoughts for several years, and doctors had 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.
Doctors deemed him as having "high risk of severe violence, perhaps even of killing someone," and Gwent Police were informed.
Mr Shorney's body was found in a park in Bargoed
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.
During the trial, David Aubrey QC, defending Royston, told the jury that if they convicted him they would hear from psychiatrists about how his mental state might have "substantially diminished his responsibility for the killing".
Royston, who did not give evidence, was also found guilty of attempting to pervert the course of justice for giving police a false alibi.
His wife Emma has already admitted attempting to pervert the course of justice for giving a false alibi and is expected to be sentenced next week.
After the trial, Mr Shorney's father Robert said he still could not believe the way in which his son had died.
He said: "I describe myself as the living dead, I'm dead inside but you can see me alive.
"What this guy had done to him - an animal wouldn't do things like this. "