Neutron activation and the JFK assassination, Part I. Data and interpretation

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Five lead fragments from bullet cores from the assassination of American President John F. Kennedy in 1963 were analyzed twice by NAA, first by the FBI in 1964 and then by Vincent P. Guinn in 1977. Their concentrations of Sb have provided invaluable information about the number and origin of bullets that hit Kennedy and Texas Governor John B. Connally. While both analyses appeared to group the fragments into a body shot and a head shot, the FBI set contained a systematic error and Guinn's results from quarters of test bullets showed that the indicator element Sb varied enough over quarters to potentially merge the groups. The latter problem was resolved by the FBI replicate analyses, which showed that antimony was nearly homogeneos on the small scales of the fragments, and by the mechanism by which jacketed bullets break when hitting bone, which generates tiny fragments from a single break near the middle of the lead core. They collectively meant that the fragments within each group were formed on the scale of subfragments. The two groups were just as they appear because the larger quarter-bullet heterogeneities did not apply. This result substantiates Guinn's original conclusion that two and only two bullets from Lee Harvey Oswald's rifle struck the two men.

This revised version was published online in July 2006 with corrections to the Cover Date.