Assessing the reliability of modern µXRF technology for expanded impact on the forensic examination and interpretation of trace evidence

Glass and tape are among the trace materials most submitted to forensic laboratories, as their physical and chemical examination can provide valuable information in forensic investigations. These disciplines use state-of-the-art methodologies that hold substantial scientific grounds and consensus-based protocols. However, some challenges come in hand with the advancements of modern technology and the changing manufacture of mass-produced materials. For example, Micro-X-Ray Fluorescence (µXRF) is an elemental analysis technique widely used in forensic laboratories that recently experienced a significant shift in their detection systems (e.g., Silicon Drift Detectors vs. SiLi detectors).  Among the advantages of SDDs are improved sensitivity and precision, which can lead to superior informing and discriminating power. However, the lagging of research in this area has not caught up with the rapid adoption of the new technology by public laboratories, exposing them to potential increased error risks.
 

Moreover, the manufacture and global marketing of glass and tape have evolved in the past years, leaving a void in current literature and datasets based on decades-old collections and instrumentation. Another challenge with µXRF examinations is the subjectivity associated with spectral data interpretation. Thus, the trace community and organizations such as the NIST-OSAC and the DOJ Forensic Science TSW have identified these research needs as a high priority.
 

This project’s overarching goal is to address these immediate operational needs by developing and validating improved protocols for collecting, examining, and interpreting contemporary glass and tape evidence. To achieve that, our multidisciplinary team (forensic practitioners in a publicly funded laboratory, forensic researchers, and statisticians) proposes to:

1) Identify the significant sources of variability when using modern µXRF SDDs and provide specific sampling and interpretation recommendations for soda-lime glass casework comparisons, 

2) Assess the accuracy, discrimination, and informing power of elemental analysis of µ-XRF SDDs of contemporary broken glass from portable electronic devices and electrical tapes, and 

3) Validate objective and quantitative metrics for µXRF spectral comparison and probabilistic interpretations of tape and glass evidence. 
 

Interlaboratory studies and the creation of an extensive dataset of over 7,000 XRF glass and tape spectra will be utilized to test error rates, providing a one-of-a-kind repository that can strengthen the current foundations and modernize standard methods.
 

This project will lead to best practices for more efficient and objective decision-making processes and increased reliability in the analysis and interpretation of physical evidence. The project deliverables are designed to have maximum impact and become rapidly adopted by forensic laboratories.