CRIME LABORATORY PROFICIENCY TESTING RESULTS, 1978-1991 .2. RESOLVINGQUESTIONS OF COMMON ORIGIN

A preceding article has examined the origins of crime laboratory profi ciency testing and the performance of laboratories in the identificati on and classification of common types of physical evidence. Part II re views laboratory proficiency in determining if two or more evidence sa mples shared a common source. Parts I and II together review the resul ts of 175 separate tests issued to crime laboratories over the period 1978 to 1991. Laboratories per form best in determining the origin of finger and palm prints, metals, firearms (bullets and cartridge cases) , and footwear. Laboratories have moderate success in determining the source of bloodstains, questioned documents, toolmarks, and hair. A fi nal category is of greater concern and includes those evidence categor ies where 10% or more of results disagree with manufacturers regarding the source of samples. This latter group includes paint, glass, fiber s, and body fluid mixtures. The article concludes with a comparison of current findings with earlier LEAA study results, and a discussion of judicial and policy implications.