A man who stabbed another inmate to death in Mountjoy jail four years ago and admitted to gardaí that he planned to get him has been found not guilty of murder or manslaughter.

Derek Glennon died after Declan O'Reilly stabbed him several times in a ground floor corridor at Mountjoy jail in June 2007.

The incident was also captured on CCTV.

O'Reilly walked free from court this evening after he was acquitted by a jury's unanimous verdict of murdering Glennon.

O'Reilly said he attacked Glennon because he was threatening and bullying him and forcing him to hide drugs, mobile phones and weapons for him.

Glennon had also punched him and threatened to have his brother shot.

O'Reilly said on the 25 June 2007 he decided to stab Glennon after he refused to take back a knife, called him a little rat and threatened to cut his throat.

Glennon died after he was stabbed in the heart, lung, stomach and arm - the CCTV footage was shown to the jury.

O'Reilly bowed his head and broke down in tears as the jury returned the not guilty verdict, following four hours of deliberations

Glennon's family immediately left the court.