10/04/2014 10:00 am ET Updated Oct 06, 2014

Teen Obsessed With 'Dexter' Given Life Sentence After Dismembering Girlfriend

Steven Miles did it just like the fictional character "Dexter" did.

He murdered his victim for the thrill, then dismembered the body and hid the parts in plastic bags. The difference between Miles and "Dexter" is that Dexter killed other serial killers. Miles killed his girlfriend and will spend the rest of his life behind bars in England, unless he makes parole after 25 years.

Miles was just 16 years old when he killed his girlfriend, Elizabeth Thomas, according to the BBC. He admitted in court that he stabbed her in the back of the head on Jan. 24 in his parents Oxted home, then chopped up her body. He put the parts in plastic bags but was arrested the same day.

He said he was trying to emulate the "Dexter" series, in which a forensics investigator turns serial killer.

"This is a case of the utmost gravity, the horrific features of which are rarely heard in any court," Judge Christopher Critchlow said before sentencing Miles this week, according to the New York Daily News.

"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."

Miles had been diagnosed with autism in the past and sought mental health services when he heard voices. Police say he told his family that his alter ego named Ed told him to murder someone.

"Ed made me do something bad," he reportedly told his sister shortly after the killing.

Miles pleaded guilty to murder on Sept. 9, ABC News reports.

Thomas was described by family members as "really pretty, really funny and really kind," Surrey Police told ABC.

CORRECTION: An earlier version of this story spelled the victim's name wrong.