Michael Behn is serving a prison sentence in the US for a murder he maintains he did not commit. In 1997, just 11 days before he went to trial, his defence team was notified that the FBI had evidence showing that bullets found in Behn's house were identical to those used to kill New Jersey coin dealer Robert Rose. His lawyers couldn't find an expert witness to dispute the bureau's testimony, and Behn got life. The assumption that bullets found at a crime scene can be matched to those in a suspect's possession has helped convict countless murderers, robbers and armed felons in the US, Britain and elsewhere. Forensic scientists analyse lead bullets for traces of antimony, tin, arsenic, copper, bismuth, silver and cadmium. The idea is that if two bullets have the same chemical signatures, they must have been made at the same time from the same batch of smelted lead. British firearms expert Jonathan Spencer, from the forensic services firm Keith Borer Consultants in Durham, says it is also common for this link to be made in court cases in Britain.
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