DNA Barcoding in Forensic Entomology: A Molecular Tool That Increases Reliability in Estimating the Postmortem Interval

Forensic entomology has become an indispensable tool for estimating the postmortem interval (PMI), particularly in advanced stages of decomposition where classical forensic methods are limited. Reliable PMI estimation requires accurate and precise identification of insect evidence. Traditional morphological approaches often fail when dealing with immature stages (eggs, larvae, pupae), closely related species, or partially damaged specimens. To overcome these limitations, DNA barcoding has been increasingly integrated into forensic entomology over the past two decades. DNA barcoding typically relies on sequencing a standardized fragment of the mitochondrial cytochrome c oxidase I (COI) gene and comparing the obtained sequence with reference databases such as BOLD and GenBank to assign species identity. In this review, we summarize the theoretical basis of DNA barcoding in forensic entomology, the genetic markers employed, and the main steps of sampling, DNA extraction, PCR amplification, and sequence analysis. We present application examples from Diptera and Coleoptera, and discuss how DNA barcoding contributes to PMI estimation and case reconstruction. Furthermore, we address recent developments such as mini-barcode strategies, Next Generation Sequencing (NGS)/metabarcoding approaches, multi-locus barcoding, and highlight key limitations including database gaps, the barcode gap concept, contamination, and NUMTs. We also evaluate the current situation in Türkiye and propose the establishment of a national barcode reference library for forensically relevant insect taxa. Overall, DNA barcoding emerges as a powerful molecular tool that complements rather than replaces morphology, thereby improving the reliability of species identification and PMI estimations in forensic casework.