It is all about the insects: a retrospective on 20 years of forensic entomology highlights the importance of insects in legal investigations

Abstract

This study highlights the importance of insect evidence by evaluating 949 insect-associated cases, including 139 entomological reports, from 2001 to 2019 at the Institute of Legal Medicine Frankfurt/Germany. With a high number of cases in the summer months and a low number in the colder season, 78.5% of the bodies were found indoors, regardless of year or month. In more than 80% of the cases, where PMI information was available (n = 704), the presumed PMI ranged from 1 to 21 days, a period during which entomological evidence can provide a day-specific estimate of PMI_min. In cases where insects have been identified to species level (n = 279), most bodies were infested by one or two species with a maximum of 10 different species. Overall, a total of 55 insect species were found. Information on biology, activity and distribution of the most abundant taxa is given and applied for 5 case histories estimating different PMI_mins of up to over 6 months. Despite proved importance and scientific development of forensic entomology, insects are still rarely considered as a tool in forensic case work. The main reasons are a lack of awareness and (too) late involvement of a forensic entomologist. Our work shows that forensic entomology is an independent discipline that requires specialist expertise.

Keywords: Blow flies; Legal medicine; Myiasis; Negligence; Postmortem interval.

Fig. 1

Number of publications with “forensic entomology” in the title, abstract or keywords published in peer-reviewed journals from 2001 to 2019

Fig. 2

Number of bodies infested with insects (bars; n = 854) found indoor (black) and outdoor (white) in the period from 2001 to 2019

Fig. 3

Number of bodies infested with insects (bars; n = 949) in the period of 2001 to 2019 found indoor (black) and outdoor (white) month-by-month

Fig. 4

Pictures of the most relevant species in forensic entomological case work. 1 Lucilia sericata: adult fly; b 3rd instar larvae; c adult specimens colonizing natural orifices (eyes, mouth) of a fresh human body. 2 Calliphora vicina: a adult fly; b 3rd instar larvae; c mono-colonization on a human body of C. vicina. 3 Chrysomya albiceps: a adult fly; b 3rd instar larvae; c mono-colonization on a human body of Ch. albiceps with zoom on the characteristic of the larvae. 4 Muscina prolapsa: a adult fly, b 3rd instar larvae; c wrapped human body with colonization of Muscina species. 5 Megaselia scalaris: a adult fly and pupa; b 3rd instar larvae; c colonization of M. scalaris on a human body with pupae stick on the face. 6 Dermestidae: a adult beetle and exuviae; b body of a 93-year-old woman colonized by Dermestes lardarius; c excrements of larvae and adult larder beetles; fibrous horsehair-like, dark-brown material

Fig. 5

Seasonal oviposition activity on human bodies of A the most important blow flies (Diptera: Calliphoridae): Aa C. vicina, Ab C. vomitoria, Ac Ch. albiceps, Ad L. ampullacea, Ae L. caesar, Af L. sericata, Ag P. regina, Ah P. terraenovae and B the most important forensically relevant flies and beetles: Ba S. argyrostoma, Bb Fannia sp., Bc Hydrotaea sp., Bd Muscina sp., Be Phoridae sp., Bf Piophilidae sp., Bg Dermestidae sp., Bh Silphidae sp

Fig. 6

Percentage distribution of indoor (black) and outdoor (white) cases for the most important and abundant species