HAGERSTOWN, Md. (AP) — Maryland’s highest court is ordering a new trial for a prison escape artist convicted of killing a Hagerstown police officer in 1975.

In an opinion filed Thursday, the Court of Appeals overturned a lower court decision in the case of Merle Unger Jr.

The court sent the case back to Washington County with instructions affirming a local judge’s ruling in 2009 that Unger deserves another trial. The Court of Appeals found that the trial judge had given erroneous jury instructions.

Unger is serving a life sentence plus 40 years for fatally shooting Donald Kline after the off-duty officer interrupted a grocery store holdup.

Unger has escaped from prisons and jails at least eight times, most recently in Florida in 1990.

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