Martin was convicted of first-degree murder with no mercy after trying to arrange a drug deal for Clp. Chuck Smith, who was working undercover for the Beckley Police Dept. Smith was shot and killed by Thomas Leftwich during the transaction.

The state Supreme Court ruled there was a serious error made during Martin's trial when a prosecution expert witness, State Police Captain Scott Van Meter, was asked by the assistant prosecutor to give credibility to the state's two key witnesses.

The High Court's opinion says the witnesses' character had not been attacked during the trial by the defense. 

"While both witnesses were subjected to cross-examination regarding various factual discrepancies, the questioning never crossed the bounds into any type of attack on the character of either witness. Even under West Virginia Rule of Evidence 608(a) the impeachment of credibility alone is not sufficient to trigger an attack on character," the Court wrote in Monday's opinion.

The opinion also says state law does not allow an expert witness "give an opinion regarding the credibility of a witness." The opinion says that's up to a jury to decide.

The Supreme Court determined Martin was prejudiced by the error and ordered a new trial. "This expert testimony improperly bolstered these key witnesses's credibility," the opinion said.

Leftwich was also previously convicted and is serving a life prison term.