Crime Library: Criminal Minds and Methods

Who Murdered Bonny Lee Bakley?

Gunpowder Residue

In the aftermath of Bonny Lee Bakley's murder, while investigators continued running down the details of her sordid past, initial reports began to surface regarding the results of Robert Blake's gunpowder residue tests. Two were administered, the most likely being a trace metal detection test and a neutron activation analysis test. Interestingly, it turned out that most of the reports circulating about Blake's tests conflicted with each other despite the fact that the LAPD steadfastly maintained that the results had not come back yet. Nonetheless, some published reports, possibly gleaned from information leaked by someone within the LAPD, indicated that the tests were inconclusive. Blake's attorney, Harland Braun, on the other hand, contended that the test results had come back negative; while still other published reports contended that the results had been positive. One account attempted to explain that if traces of gunpowder residue had been found on Blake it was because he had been target practicing recently with the gun he was carrying to protect his wife due to her belief that her life was in danger. At one point it was even said that the FBI was studying the results of those tests for the LAPD and that detectives were waiting for the FBI's report.

In practicality, the long and the short of it was that the gunpowder residue tests might have no forensic value at all to the investigation. For example, if the trace metal detection test was administered, it can be determined whether or not a person has recently been in contact with metal. Big deal. In that test, if Blake had touched any metal at all in the hours before the test was administered, the test results could come back positive, which would prove nothing other than that he had touched metal. He could have easily done that by opening the front gate at his house or by opening the car door for Bonny. If a more specific type of test was administered, such as the one in which the investigators look for the presence of barium and antimony and which encompasses neutron activation analysis, a positive test result could indicate whether the person being examined was contaminated with "blowback" residue from having recently fired a weapon. Such residues are typically removed from the subject by swabbing the back of the index finger, thumb and the web areas of the hand with a moistened cotton swab containing a solution of five percent nitric acid. But again, the value of such an examination is questionable since barium and antimony are found in nature, as well as in a variety of common products, and it was always possible that the subject being examined had come into contact with those elements from sources other than firing a gun. Most such tests are inconclusive because the individual who administers the test cannot state with an adequate degree of positivity that the subject had fired a gun. Even when such test results come back positive, a suspect's defense lawyer can bring in other forensic experts who can challenge or dispute the original findings based on different interpretations of the test results. Because of the ambiguity associated with such tests, a prosecutor's case can actually be damaged if the test results are not backed up with sufficient additional forensic evidence that points toward the suspect's guilt.

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