Cardiff prisoner died after being stabbed in neck with pen
An inmate at Cardiff prison died after his cellmate stabbed him in the neck 100 times with a ballpoint pen, a murder trial has been told.
Colin Capp, 23, attacked Darren Thomas, 45, while he slept in their cell on Wing B at the prison.
Cardiff Crown Court heard he wrapped a plastic bag around his head and stabbed him repeatedly in the neck with a pen.
Mr Capp, from Scotland, admits killing his cellmate - but denies murder claiming "diminished responsibility".
Prosecutor Peter Rouch QC said: "Darren Thomas had around 100 puncture marks to the left side of his neck.
"He died from sustained application of significant pressure to the neck - his death was caused by strangulation, suffocation or both.
"It's abundantly clear that Mr Capp intended to kill Darren Thomas.
"He understood what he was doing and his ability to exercise self control was not substantially impaired."
Mr Thomas had just started a 12-week sentence at HMP Cardiff for breaching an ASBO banning him from entering Cardiff city centre.
He was put in a cell with Mr Capp - an arsonist who had been recalled to prison after checking himself in to a psychiatric ward saying he was thinking of starting more fires.
The pair had been risk assessed about whether they would make suitable cellmates at the prison.
Prison officers went to their cell in the middle of the night after an alarm went off and found Mr Thomas with a plastic bag wrapped around his head.
Mr Capp told prison staff that Mr Thomas had threatened him with a plastic knife earlier in the day and said: "I needed to do him before he did me."
Mr Capp denies murder and the jury was told that they will hear from psychiatrists who have assessed him.
The trial continues.