3 November 2015 Last updated at 18:58 GMT
Sussex Police has released footage of Oliver Parsons filmed on an officer's body-worn camera after he was arrested in Brighton.
Parsons said victim Joe Lewis was a bully who "tried to take over" the flat where he was stabbed to death.
He has been jailed for life, with a minimum of 16 years in prison, after pleading guilty to murder at Lewes Crown Court.
A man who murdered another man in the early hours of Christmas Day, 2014 told police he was a psychopath and did not care if the man died.