Proposed practices for validating the performance of instruments used for automated inorganic gunshot residue analysis

The reliability of forensic inorganic gunshot residue (iGSR) analysis depends strongly on the performance of the scanning electron microscope with energy dispersive X-ray spectrometer (SEM/EDS) instrument and the software that automates the data acquisition. Without a record of the baseline performance of the instrument, it is often hard to know when performance has deteriorated. This paper provides a set of tests which can be performed when the instrument is commissioned, or when significant modifications are made, to establish the baseline performance and a smaller set of tests that can be performed regularly to document the current performance of the instrument. Together, these represent a powerful way to establish, document and evaluate the performance of the instrumentation used for iGSR analysis. Furthermore, most of these tests are suitable for characterizing SEM/EDS instruments used for other forensic or non-forensic uses.