Police have thanked witnesses for helping them get justice for a teenager who was murdered.

Charlie Cosser, 17, was stabbed at an end-of-term party at a farmhouse in Marches Road, Warnham, near Horsham, last July 23.

Charlie, also known as Cheeks, suffered a cardiac arrest on the way to the Royal Sussex County Hospital where he died on July 25.

His killer, who was 16 at the time and is now 17, will face life imprisonment for the attack following a trial at Lewes Crown Court, sitting in Brighton.

The Argus: Charlie Cosser and his dad Martin who has been campaigning against knife crime since his son's deathCharlie Cosser and his dad Martin who has been campaigning against knife crime since his son's death (Image: Martin Cosser)

The teenage defendant, who cannot be named for legal reasons, was found guilty of Charlie’s murder and having a bladed article in unanimous verdicts on Tuesday.

READ MORE: ‘Nothing will bring back my son’ – Family’s heartbreak at boy’s murder

Members of Charlie’s family, who attended court every day during the three-week trial, cried and hugged each other as the verdicts were given.

Senior Investigating Officer Detective Chief Inspector Kimball Edey, of the Surrey and Sussex Major Crime Team, said: “Our thoughts continue to be with the family, friends and loved ones of Charlie following this devastating incident.

“This was a complex and fast-moving investigation. We are grateful for all the public’s support and for the witnesses who came forward to help ensure we got justice for Charlie."

The defendant has been remanded in custody, to appear for sentencing on June 19.