Chitra Ragavan Reports On The Allegations Of Improper Procedures at the FBI's forensic lab. She talks with outspoken whistleblower Frederick Whitehurst. He says that other agents contaminated and misplaced evidence... sometimes in such high profile cases as the Oklahoma City bombing. Whitehurst says his own lab reports were changed by superiors to make the lab look good and to help prosecutors. The FBI denies the charges. The agency now has to respond to the Justice Department, following a year-long investigation.