Comparative Bullet Lead Analysis

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The Comparative Bullet Lead Analysis (CBLA) is a forensic technique in which an attempt is made to establish an assignment to a specific production batch or ammunition box via the chemical composition of bullets .

functionality

Lead bullets are cast or pressed using lead or lead alloys. A large number of projectiles are made from the same lead melt. The CBLA assumes that:

  1. the lead melt of a batch has a completely uniform chemical composition
  2. no two lead melts have the same chemical composition and therefore each lead melt is chemically unique

A projectile found at the scene of the crime should be clearly assigned to other ammunition that may have been found in suspicious persons.

Application and detection of lack of evidential value

The CBLA was first used in 1963 after the death of US President John F. Kennedy and has been used to convict suspects in several thousand cases for more than 40 years. In 1998, the former chief metallurgist of the FBI William Tobin found in private studies that bullets from one batch are not chemically uniform and that bullets from the same box are not chemically identical. According to Tobin, it is statistically possible that there are ten million identical copies of every bullet made in the USA, which means that the CBLA is forensically useless. Dwight Adams , then head of the FBI Lab, asked the National Academy of Science in 2002 to conduct an independent evaluation of the CBLA method. According to the report, released 18 months later, the CBLA is unreliable and potentially misleading for the purpose of evidence. The technique has not been used by the FBI since 2005.

It is estimated that the CBLA has been used in approximately 2500 cases. Research by the Washington Post and 60 Minutes found 250 cases. A well-known case of someone convicted with the help of the CBLA is Wayne Lee Hunt who was convicted of a double homicide in 1985.

Web links

Individual evidence

  1. ↑ Bullet-Lead Analysis: No Longer A Smoking Gun washingtonpost.com, November 17, 2007
  2. ^ Christian Galuschka: Die Ballistiker Telepolis, November 21, 2007
  3. ^ John Solomon: FBI's Forensic Test Full of Holes washingtonpost.com, Nov. 18, 2007