Martin, 19, of Heath Way, will serve a minimum of 15 years.

He was found not guilty of wounding another teenager, who can't be named for legal reasons, with intent to cause him grievous bodily harm -but found guilty on a lesser charge of wounding.

Judge Richard Brown said: "This was in my view an horrendous and mindless attack on a young man who was posing no threat whatever to you.

"Not only have you taken the life of a perfectly respectable 15 year old boy - you devastated the lives of his family and friends."

Martin was asked to leave a fancy dress party in Gorringes Brook, Horsham, on November 3 last year.

He left, but came back with martial arts nunchuks and attacked Ricky, hitting him around the face and head. The other teenager was injured when he tried to intervene.

Ricky was taken to East Surrey Hospital, in Redhill, then transferred to St Georges Hospital, in Tooting, London, where he was pronounced dead from a fractured skull and internal bleeding.

Martin will run a four-year concurrent custody for the wounding charge with a one year extension. The 295 days in custody will count towards the sentence.

Follow how the trial went below.

Martin had crossbow and airgun.

Ricky Butler murder trial latest - Martin admits manslaughter

Ricky Butler murder trial latest - friend's call to Martin after attack

Ricky Butler murder trial latest - Martin's martial arts 'interest'

Ricky Butler murder trial latest - Ricky's last moments

Ricky Butler trial latest - pathologist gives evidence

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