Doubts About the Expertise of Forensic Evidence

The television program, 60 Minutes, and the Washington Post are doing an investigation of a failure of the FBI labs, which for decades produced metallurgical results implicating bullets from victims as coming from the same lot as ammunition found in the possession of suspects. Turns out the analysis was not trustworthy, and the FBI has stopped using the techniques, but has not yet notified the people convicted based (in part) on "expert" testimony overstating the validity of the metallurgical evidence. Today's article in the WP describes a case in which the tainted metallurgical evidence was combined with questionable DNA evidence (possibly contaminated samples which were not cleaned before analysis), doubtful (and possibly misrepresented) evidence implicating the suspects revolver offered by a State employed witness who falsified his credentials, questionable blood evidence, and in which alibi evidence was not accepted.

Comment: It is unfortunate when too much reliance is placed in the judiciary process on the value of expert testimony. Non experts must consider the quality of the forensic science, and the credibility of the persons presenting that evidence.

Thus it is especially important that government agencies that are responsible for forensic science maintain the highest quality standards, and are punctilious in the tests that they authorize and the evidence they present. They should not only assure the professional qualifications of their staffs, but also have strong programs to assure the ethical conduct of staff, especially when offering testimony.

It is especially important that the criteria used in assessing the performance of forensic scientists and laboratories be well conceived. They should not be given credit for convictions, but rather for accuracy of results and scientific quality of testimony.

The prosecutors faced with a posteriori evidence that some of the evidence presented in past trials is tainted have a difficult task. They must decide whether the evidence was important in the jury's decision, and their incentives are to convict criminals.

The courts have the responsibility to make the system work. Judges should themselves be knowledgeable about the quality of forensic evidence in the cases that they try, should keep the advocates honest, should help keep the expert witnesses to present their evidence fairly, and should help juries to evaluate forensic evidence and the cridibility of expert witnesses well. JAD