Logan MacPhail, 17, has been jailed for life with a minimum term of 17 years for murdering his ex-girlfriend Holly Newton, 15, after he stalked and then stabbed her to death in January 2023.
Holly suffered 36 injuries in just over a minute during a knife attack in an alley in Hexham, Northumberland.
CCTV showed MacPhail wearing a snood and a baseball cap and ducking out of sight as he followed Holly and her friends around the town centre.
He also stabbed a teenage boy who intervened to try to stop the attack.
MacPhail was convicted of murder following a trial at Newcastle Crown Court, and was sentenced at the same court on Friday.
This is a breaking news story and it is being updated