Getting grotty with insects (not for the squeamish)

By Anna Sandiford 18/02/2011

Some forensic scientists have jobs the rest of us could never even imagine, never mind do straight after breakfast.  Take forensic entomology for example.  Its use in suspicious death cases is well known through authors such as Patricia Cornwell and through programmes like Bones and the many versions of CSI, particularly Las Vegas where Grissom was a forensic entomologist (apparently, he’s making a comeback). 

In real life, forensic entomology enables investigators to link corpses at various stages of decomposition with time since death.  The variety of insects found can also reflect location of the person when they died or movement after death.   That in itself is fascinating and, to some, repulsive. 

This blog post is based on a case study prepared by my colleague, Dr John Manlove of MFL in England.  One of his roles as a forensic entomologist involves dealing not only with corpses but also cases of living host infestation (myiasis).

In the same way that insects are attracted to the bodily fluids and decaying tissues of and around a corpse, some feed and complete their life-cycle on a living host if the conditions are ‘favourable’. Although often considered to be restricted to animals (cattle and sheep), myiasis can also occur in humans where the host is still alive during the insect feeding and infestation process. Not only can this have an implication for calculating the post mortem interval (time from death to the time body is found), it can also reflect cases of abuse and neglect.

Myiasis can be a reliable indicator of when humans may have been kept in squalid conditions, where unhygienic environments have occurred in hospitals, or even in cases of personal hygiene. One area of particular relevance is that of social care, with the elderly. In fact, I had a case enquiry a couple of weeks ago from a lady who was concerned about her elderly friend because maggots had been found in her friend’s clothing when she was recently taken to hospital. It also occurs in instances of probable child abuse.

The case study I mentioned involved scene examination of a recently-deceased young child. In-situ sampling by entomologists recovered the majority of entomological specimens from the face and genitalia. It was clear that the specimens encountered in the face of the child were of a different species and age from those found both inside the nappy and within the body of the child itself.

The insects recovered from the genital region were a species known to live and reproduce in urine and faeces and would have been attracted to a soiled nappy. The child would not have been old enough to maintain personal hygiene, relying totally on a carer, and would have been helpless to prevent adult flies laying their eggs. The resultant larvae that hatched thrived well in such an environment.

The insects recovered from the face of the child (eyes, nose, mouth) were typical of those commonly encountered on corpses (blowflies) and were at an earlier stage of development and therefore younger than the species found in the nappy (houseflies). Not only did this have implications for calculating the post mortem interval but it also provided potential evidence of neglect by the mother.

Despite this seeming to be amongst the most disturbing applications of science in forensics, in this case the sampling, examination and interpretation of the insects was neither time-consuming nor expensive and ended up being very helpful in resolving the case.

It’s not pretty, but it has to be done.