DETROIT (WWJ/AP) – The Michigan Supreme Court has turned down an appeal by a Detroit-area drug dealer known as “White Boy Rick,” who wants a new sentence after nearly 30 years in prison for crimes as a teen.

The court let stand an appeals court decision that said Richard Wershe Jr.’s sentence can’t be set aside because it was a legal punishment. The order was released Thursday.

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The 46-year-old Wershe has been in prison since he was 18. He was convicted of possessing more than 650 grams of cocaine and given a life sentence. He’s been eligible for parole, but the parole board hasn’t released him.

A Detroit-area judge last year said Wershe was entitled to a new sentence, noting his age at the time of his crime and other circumstances. But that decision was overturned.

Wershe’s story made headlines around the world when he infiltrated local drug gangs at the tender age of 13 — at the request of Detroit police and FBI agents — and turned in evidence that convicted 14 dealers and gangsters, including some of the biggest drug dealers in Detroit history.

His attorney, Ralph Musilli, has claimed that as a direct result of Wershe’s help, the FBI was able to infiltrate a gang of Detroit police officers that was transporting drugs from the Wayne County Airport to the streets of the city’s east side.

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The then-baby-faced teen was sentenced to mandatory life prison under the state’s strict cocaine dealing laws.  The Michigan constitution was later amended to lighten up sentences for nonviolent offenders — yet Wershe’s release has continued to be denied.

The appeals court maintains that Wershe was given a “valid sentence,” and any attempt to give him a new sentence conflicts with the powers of the parole board.

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