This spring Oklahoma City learned that one of the city's top forensic chemists had for years been giving flawed testimony in criminal trials. Now a man on death row has had his death sentence overturned.

A federal appeals court today overturned the death sentence of Alfred Brian Mitchell, saying that false DNA evidence provided by the chemist, Joyce Gilchrist, might have influenced the jury's decision to impose the death penalty.

Mitchell had been convicted of murder, rape and sodomy in the 1991 death of college student Elaine Scott. In 1999, a lower federal court overturned the rape and sodomy convictions after hearing that, contrary to Gilchrist's testimony, there was no DNA evidence that Mitchell raped Scott before killing her.

The lower court allowed the murder conviction and the death sentence to stand, saying there was sufficient evidence without the rape conviction to justify the death penalty.

But the appeals court disagreed. "We simply cannot be confident that the jury would have returned the same sentence had no rape evidence been presented to it," the judges wrote. Mitchell will now face resentencing and may be spared the death penalty.

22 Other Death Cases Still Under Review

Mitchell is one of 23 defendants whom Gilchrist helped send to death row during her 21 years with the Oklahoma City Police. Eleven of the condemned men have been executed.

A formidable presence in local courtrooms, Gilchrist gave testimony on hair, semen, blood and fabric in thousands of cases.

But there was suspicion about her testimony for years. At the request of local police, the FBI reviewed a random sample of her work earlier this year. Of eight cases examined, six were found to be seriously flawed. The confidential FBI report was scathing, saying that Gilchrist "made statements that went beyond the acceptable limits of forensic science."

In May, one of the six cases faulted by the FBI ended in the release of a wrongly convicted man after he served 15 years in prison for rape. The man, Jeffrey Todd Pierce, was freed after DNA tests showed that sperm and hair found at the scene were not his. At the 1986 trial, Gilchrist had testified that the hair belonged to Pierce.

Local police and the FBI are now reviewing the 22 other death row cases in which Gilchrist testified. This spring local prosecutors assured the public that Gilchrist's role in all the death row cases was insignificant and would not have affected the outcome. This week the federal appeals court disagreed.