Genetic markers detectable in bloodstains include six different red cell markers, four serum markers, and nine different red cell enzymes. This great potential for detecting evidence from bloodstains offers more evidence towards both exonerating the innocent and convicting the guilty. Defense lawyers typically need expert help in examining materials not examined by the prosecution, retesting the results obtained in tests by the prosecution, tests for further blood groups not checked by the prosecution, and an interpretation of the results of the prosecution's tests to determine if anything helpful to the defendant is being left unsaid. Out of 113 cases referred to the London Hospital Medical College's Departments of Forensic Medicine and Hemotology (England) during the years 1975-1979, at least 10 percent have resulted in a favorable outcome for the defense. These favorable outcomes include acquittal, charges dropped, evidence withdrawn, or substitution of a lesser charge. Data tables pertaining to favorable results in specific trials are included.