A DNA Barcoding Strategy for Blow and Flesh Flies Encountered During Medicolegal Casework

Accurate insect identification is critical to their use in estimation of time of colonization (TOC) and post-mortem interval (PMI) during medicolegal death investigations. Insect specimens are currently identified by evaluating morphological characteristics as indications of particular taxonomic groups; however, this process is limited because immature life stages typically lack distinguishing morphologies. These deficiencies may be addressed through molecular identification by DNA “barcoding” wherein DNA sequences from unknown samples are matched to references. This technology enables identification of immature specimens, may be performed without specialized forensic entomology training, and requires equipment common to forensic genetics laboratories. DNA barcoding has been demonstrated in numerous entomological surveys of forensically relevant species; however, the technology has not been implemented for medicolegal death investigations. This is due in part because of deficiencies in the technology: no single primer set is capable of distinguishing all of the diverse species important to forensic investigations. Instead, multiple primer sets and sequencing reactions are utilized to maximize the species that may be identified.
We propose an optimized DNA barcoding strategy to simplify species identification for use during medicolegal death investigations. We propose analysis of a single locus capable of distinguishing insects commonly encountered in casework across the United States, in particular, blow and flesh flies of families Calliphoridae and Sarcophagidae. We propose experiments demonstrating complementation with forensic entomology practices by enabling identification of unknown immature specimens encountered during casework. Internal validation studies will be performed adhering to the FBI Quality Assurance Standards for Forensic DNA Testing Laboratories and ISO/IEC 17025 International Standards. Protocols for performing DNA barcoding for medicolegal casework will be implemented at the Harris County Institute of Forensic Sciences (HCIFS) Forensic Genetics Laboratory. The frequency and impact of DNA barcoding of blow and flesh fly species encountered will be communicated to law enforcement and forensic practitioners at national meetings and through publications.

Note: This project contains a research and/or development component, as defined in applicable law, and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14).

CA/NCF