Abstract
ABSTRACTForensic entomology evidence collected by police and mortuary staff may be delayed in getting to the entomologist. Live samples may continue developing and alter minimum postmortem interval (PMImin) estimates. This study investigated development of simulated evidential samples of Calliphora vicina Robineau-Desvoidy and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) maggots. Maggots of each species were studied in three developmental classes: “small” (late second/early third instar), “mid” (mid third instar) and “large” (late third instar). Seven replicates of 11 maggots in each class were assigned without food to four treatments: (1) 24 h at 20 °C; (2) 24 h at 4 °C; (3) 48 h at 20 °C and (4) 48 h at 4 °C. There was a significant difference in absolute length change across treatments, reflecting size for C. vicina, and interaction between size, time and temperature for Ch. rufifacies. Calliphora vicina maggots showed minimal mortality, and most second instar larvae moulted by the experiment's end. Chrysomya rufifacies showed heavy mortality and minimal moulting from the second to third instar. Only “large” Ch. rufifacies maggots kept at room temperature for 48 h pupariated. Since these results confirm that development can continue in live unfed maggot samples after their collection, it is not advisable to delay their preservation.
Highlights
Impeccable evidence collection is at the heart of a solid forensic opinion, and failure to follow protocol can result in serious consequences in court [1,2]
There are various types of evidence collection problems, which include contamination, incomplete collection, incorrect sample handling, deviation from accepted protocol and delayed delivery of perishable or live evidence to analysts. These problems have beset a variety of forensic science disciplines, prompting numerous papers that provide instructions for optimal evidence collection and training standards, thereby outlining “best practice” [3,4,5,6]
“Small” C. vicina maggots grew from baseline length, whereas “large” maggots decreased in length, especially at room temperature
Summary
Impeccable evidence collection is at the heart of a solid forensic opinion, and failure to follow protocol can result in serious consequences in court [1,2]. There are various types of evidence collection problems, which include contamination, incomplete collection, incorrect sample handling (e.g. lack of secure and environmentally controlled storage conditions, inadequate chain of custody), deviation from accepted protocol (including use of non-validated or incorrect methods) and delayed delivery of perishable or live evidence to analysts. These problems have beset a variety of forensic science disciplines, prompting numerous papers that provide instructions for optimal evidence collection and training standards, thereby outlining “best practice” [3,4,5,6]. Proxy collectors are only infrequently asked to collect entomology evidence, and may be prone to mistakes caused by inexperience
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