The effect of killing and preservative solutions on estimates of maggot age in forensic cases

Length of the oldest maggots recovered from a body often provide an accurate estimate of the time since death. The length of maggots of Protophormia terraenovae (Robineau-Desvoidy) of known age, at peak of feeding, was measured after 5 days immersion in one of 15 killing and preservative solutions, some of which are routinely used at autopsy and in forensic entomology; controls were killed in boiling water. There was shrinkage in all 15 solutions which translated into an underage error of 9.7 h in 70% ethanol, 11 h in San Veino and 16.8 h in formalin. Larvae of Calliphora vicina (Robineau-Desvoidy) underwent even greater shrinkage, which resulted in an underage error of 19.2 h in 70% ethanol, 26.4 h in formalin and 28.8 h in San Veino. Young third instar larvae underwent more shrinkage than older ones, with underage errors (in hours) as follows: P. terraenovae-70% ethanol 24 and San Veino, 24; C. vicina-70% ethanol, 7.2 and San Veino, 14.4. Maggots killed in boiling water and then placed in preservative solutions did not shrink. Length of the crop, which may be useful in age estimates of postfeeding larvae, was not altered significantly for forensic purposes in these solutions. The highly significant alterations in maggot length underscore a need for standardization in the treatment of maggots collected at the crime scene and at autopsy if their length is to be interpreted in a valid and consistent way. Recommendations are made for treatment of maggots wherever they are collected.