Joseph Cox* | Florida International University Katherine Davis, Kylea Morris, Rachel Mohr, and Luis E. Arroyo-Mora | West Virginia University Joseph DelTondo | Allegheny General Hospital Abstract: Beyond 72 hours, entomological evidence is considered the most reliable source to estimate the minimum postmortem interval (minPMI), the minimum amount of time that it would take for an insect to reach a physical characteristic such as length or life stage. The succession that occurs on a corpse after death is a relatively confined and closely packed ecosystem that is typically restricted to the remains and environment proximity. The incorporation of drugs into the insects is possible and opens an opportunity for assessing drug presence and developmental effects in insect tissue. If drugs are present when the insects are actively feeding, their size or stage of growth could be impacted and ultimately lead to an incorrect minPMI calculation. This study investigates the effects of fentanyl on the development of blow fly (Lucilia sericata) larvae and the ability to detect and quantify the drugs or metabolites present in each stage of the fly’s life cycle. The researchers evaluated human tissue fortified with fentanyl at four treatment concentrations. Blow fly larvae were placed to feed on the drug- infused tissue then collected at seven time frames. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method was developed, validated, and applied to extract fentanyl and metabolites from the larvae, pupae, pupae casings, and adult flies. This research represents an advancement for forensic toxicology laboratories and medical examiner’s offices for complex biological matrices by providing (1) a validated protocol to extract and quantify fentanyl and metabolites from complex matrices using QuEChERS, (2) an evaluation of any growth effects fentanyl has on the development of the insects and the potential implications for minPMI estimations, and (3) conclusions on the ability to correlate the concentration of fentanyl and metabolites from the insect tissue to the initial concentration of the feeding media.