CHICAGO (CBS) — An Illinois appeals court has affirmed former Bolingbrook police officer Drew Peterson’s conviction and prison sentence in the murder of his third wife, Kathleen Savio.

Peterson is serving a 38-year sentence for killing Savio in 2004. Although her death initially was ruled an accident, authorities reopened the case after Peterson’s fourth wife, Stacy, disappeared in 2007. Savio’s body was exhumed, and a new autopsy ruled Savio’s death a homicide by drowning.

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In 2012, a Will County jury convicted Peterson of drowning Savio in her bathtub. Prosecutors had argued he killed her to prevent her from testifying against him in divorce proceedings.

Peterson appealed his conviction and sentence, arguing prosecutors did not prove him guilty beyond a reasonable doubt, his trial attorney operated under a conflict of interest, and he was denied effective counsel. He also said he was denied a fair trial due to numerous errors by the trial judge.

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A three-justice panel of the Third District Illinois Appellate Court upheld Peterson’s conviction on Thursday, stating the evidence against him was sufficient to prove he killed Savio.

In a unanimous opinion, the court said it found no errors at trial, and that the physical and circumstantial evidence presented in court proved Peterson was the killer. The justices also rejected Peterson’s claim that his lead trial attorney, Joel Brodsky, had a conflict of interest due to media contracts he signed before trial.

“This is the ultimate vindication of this eight-year journey we’ve been on,” said Will County State’s Attorney James Glasgow, who prosecuted the case.

Defense attorney Steve Greenberg said he would file a further appeal.

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Peterson is awaiting trial on charges he tried to hire a hitman to kill Glasgow after Peterson was sent to prison.