Image copyright Surrey Police Image caption A-Level student Elizabeth Thomas was found stabbed to death at a flat in Oxted

A teenage boy obsessed with a TV serial killer has been jailed for at least 25 years for murdering and dismembering his 17-year-old girlfriend.

Guildford Crown Court heard Steven Miles stabbed Elizabeth Thomas to death before cutting up her body with saws in his bedroom.

He was arrested at the scene in Amy Road, Oxted, Surrey, on January 24.

Jurors heard Miles, 17, who admitted murder, had a fixation with the lead character in the US series Dexter.

He was given a life sentence and told he must serve at least 25 years before being considered for release.

'Told to kill'

Image copyright Surrey Police Image caption Steven Miles had an obsession with a fictitious TV serial killer

The teenager told his family that a voice in his head named Ed told him to kill someone.

He used tools from his father's tree surgery business to cut up his girlfriend's body before wrapping her dismembered limbs and placing them in bin bags.

When Miles' sister returned to the family's flat about an hour after the murder, he told her "Ed made me do something bad."

Psychiatric experts told the court "Ed" was likely to be a manifestation of anxiety, rather than schizophrenia, said BBC South East Home Affairs correspondent Colin Campbell.

Miles had some narcissistic personality traits and showed signs of being on the autism spectrum, and the court was told it was these traits that are likely to have caused the anxiety, he added.

The court was told Miles had a fascination with horror movies and had wanted to copy the actions of Dexter, the main character in an American TV series about a police forensics officer who is also a serial killer.

Prosecutor Philip Bennetts said Miles' parents, Emma and David Miles, had referred him to his GP and mental health services after he began to self harm in April 2012.

Ex girlfriend 'strangled'

After missing an extended period of school and undergoing support for his condition in October 2013 he was judged as having made good progress and was discharged by the mental health services.

One of his previous girlfriends told police he had described how he was going to kill someone and that on one occasion he tried to strangle her for a matter of seconds.

Judge Christopher Critchlow said: "This is a case of the utmost gravity, the horrific features of which are rarely heard in any court.

"Nothing this court can say or do, no sentence this court can impose can alleviate the pain suffered by Elizabeth Thomas' family for death in such a terrible manner. There must be a life sentence."

Elizabeth's family described her as a "kind, caring, loving and gentle girl".

She grew up in West Wickham, south-east London, and had been studying at Oxted School for her A-Levels at the time of her death.

Image caption Miles killed Elizabeth in his family's flat before dismembering her

Correction 9 October: This story has been amended to reflect more detail of the psychiatric reports on Steven Miles.