Jeffrey Pierce spent 15 years in prison in Oklahoma for a rape he did not commit. DNA testing finally proved that the trial testimony of an Oklahoma chemist was false. The chemist, Joyce Gilchrist, testified that she had matched hair and semen samples from the crime scene to Mr. Pierce. Now, hundreds of cases in which she testified will come under review. NPR's Eric Westervelt reports Ms. Gilchrist is not the only scientist and hers is not the only crime lab under scrutiny.