In 2004 and 2006, researchers at Lawrence Livermore Laboratories in California showed that there was much more variability in Guinn's analysis in the levels of trace metals, like silver and antimony. The major problem with the analysis resides in the data analysis and interpretation of the results. In 2002 the FBI enlisted the help of the National Academy of Sciences' National Research Council (NRC) to conduct an independent study of the bullet lead analysis method, using independent experts in the field. The NRC's final report expressed significant concerns over the interpretation of bullet lead examination. The FBI still stands by its procedures as being valid for evidence purposes. However, this and other data has led the FBI laboratory to announce officially in September 2005 the discontinuation of bullet lead examinations. Since then, this evidence has been suppressed by courts in several states and will undoubtedly be challenged in a great number of future cases.
Kennedy Assassination Fragments Revisited
Because of the historic significance of the bullets fired in Dallas that day, bullets from the same brand and lot as used in the assassination have been preserved as collector's items and are still available today. A group of researchers at Texas A&M University have undertaken a project to reanalyze these bullets by more modern procedures, because they believe it is desirable to reevaluate the evidentiary value of this data. The group includes researchers William James and Cliff Spiegelman, and the FBI Laboratory's former chief metallurgist, William Tobin. Tobin, before his retirement, has been involved in a multitude of analysis projects including the bombing of the Murrah Federal Building in Oklahoma City and the crash off Long Island of TWA Flight 800. He has for many years questioned the FBI's methods used to match bullets to crime suspects.
After the NRC's report, the National Academy of Sciences developed new guidelines for accurate and proper bullet analysis. Following these guidelines, Tobin and his co-workers reanalyzed the evidence presented to the House Select Committee on Assassinations in 1976. This was the evidence that determined that a lone shooter (Oswald) was Kennedy's killer.
Five bullet fragments were used in the analysis by the FBI lab and Guinn. These were retrieved from Kennedy's body (2), Connally's wrist (1), the bullet on the stretcher at the hospital and from the Presidential limousine (2). In an article recently published in the Annals of Applied Statistics, these authors conclude that "the evidence [antimony levels] used to rule out a second assassin is fundamentally flawed". Based on careful statistical analysis of the trace metal data, they believe that Guinn used an analytical method and certain statistical assumptions that were faulty. They further assert that their findings "mean that the bullet fragments from the assassination that match could have come from three or as many as five separate bullets".
Tobin and his colleagues do not definitely conclude that more than one shooter was present that day in Dallas. However, they do say "that if the fragments came from three or more separate bullets, then a second assassin is likely, as the additional bullets would not be attributable to the main suspect, Mr. Oswald".
Forensic analysis is a dynamic science and new instrumentation and methods are always being developed to provide more and better quality evidence. Sometimes, as in this case, data from older methods may have to be reevaluated. It is important for law enforcement officers and prosecutors to remember that forensic evidence is only a part of the puzzle. It should not be the only evidence on which a case is based. Forensics cannot replace basic investigation procedure and evidence gathering; it can only supplement it.