Problems of the SPring-8 Forensic Analysis of Sumitomo Metal Mining As₂O₃ 25-Lots at the Wakayama Arsenic Curry Incidence

Abstract

Problems of synchrotron radiation X-ray fluorescence (SR-XRF) analysis is studied based on the forensic analysis of the Wakayama Arsenic Curry Murder Incident. In this case, 25 cans of As₂O₃ produced by Sumitomo Metal Mining Co. Ltd. were measured by Prof. Nakai at SPring-8 BL08W in order to prove that the concentration of impurity element Sb was changed as the change of cans. Nakai concluded in his forensic report that the relative intensity of Sb was different when the can was different. However Sb concentration of 9 of 25 cans were 120 ppm, which were analyzed by ICP-AES, and some of them were testified different by Nakai. On the other hand, some were tesfified as same concentration in spite that the concentrations were different. Based on Nakai's forensic report as well as on the testimony, the judge concluded that the arsenic poisoned the curry was identical to that of the arrested houswife and sentensed death penalty. The precision of SR-XRF is also checked for another forensic report, and again the precision was not enough for identification.