Harrison and Gilroy Method

In 1959, Harrison and Gilroy introduced a method based on the detection of the metal-containing components of FDR.124 The metallic components involved, namely, lead, antimony, and barium, originate from the primer and the bullet (lead and antimony). The method is based on colorimetric spot tests and involves swabbing the suspect's hands with cotton cloth damped with 0.1 M hydrochloric acid. The swab is allowed to dry and is then tested with one or two drops of a 10% alcohol solution of triphenylmethylarsonium iodide. The appearance of an orange ring indicates the presence of antimony.

The swab is then dried again and treated with two drops of freshly prepared 5% sodium rhodizonate solution to the center of the orange ring. The development of a red color indicates the presence of lead and/or barium. The swab is then dried a third time in the absence of strong light, and one or two drops of 1:20 hydrochloric acid are added to the red colored area. A blue color developed inside the orange ring is confirmation of the presence of lead. A red color remaining in the center confirms the presence of barium.

These tests were considered to be inconclusive, and the sensitivities of the colorimetric reagents used were not adequate to reliably detect the low concentrations found in actual firings.125-129

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