A TEENAGER admitted to murdering his twin sister after claiming he stabbed her to death when he was sleepwalking.

Benjamin Elliot, then 17, fatally attacked Meghan while she slept in the family home before immediately phoning the cops as soon as he woke up.

In a chilling call, Benjamin confessed: "I just killed my sister. Oh my God … I thought it was a dream."

Benjamin, now 21, said he was a frequent sleepwalker but had never been violent during a nighttime episode in the past.

Despite his pleas of innocence, the young man was made to stand trial for murder.

He was found guilty and sentenced to 15 years in prison in February.

CBS News 48 Hours correspondent Erin Moriarty spoke to a caged Benjamin about the case earlier this year.

She asked how he could be so sure he was sleepw

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