While scientific evidence is often very compelling and can be a prosecutor’s “ace-in-the-hole,” the justice system needs to be on guard for experts who fabricate results, use shoddy testing techniques, or testify outside their areas of expertise. Recent problems with tampering and fabrication by forensic experts have lead to the review of thousands of cases. However, in some of these cases, particularly capital cases, this review comes too late. When such allegations come to light they often shake the public’s faith in the justice system.