Jonathan J. Koehler. Forensic science—which includes such techniques as DNA analysis, fingerprint examination, and firearms comparison—plays a crucial role in our criminal justice system by helping to convict the guilty and acquit the innocent. However, our confidence in forensic science conclusions must be tempered by the odds that those conclusions are wrong. What are those odds? Nobody knows the answer because no disinterested researchers have conducted the appropriate studies in any of the forensic science disciplines. This is a serious problem because, without this information, legal decision makers cannot properly assess the validity or probative value of forensic evidence. In this paper, I examine the institutional forces and misunderstandings that are responsible for our ignorance about the accuracy of forensic science conclusions. I then recommend a new type of proficiency testing regimen (Type II proficiency testing) that is designed to measure error rates under appropriate test conditions in the various forensic subfields. Unless and until such studies are undertaken, legal decision makers will continue to fly blind when it comes to assessing the reliability of a reported forensic match.