When new knowledge on moth munching helped convict a double-murderer
Forensic entomology is not for the faint-hearted. While insect-related evidence has been known to be used in the odd civil case, for the most part, it’s about creating a narrative around human death, often in grisly circumstances, based on insect feeding and reproduction on, in and around cadavers.
It requires a certain sort of constitution, and its decidedly dark edge means it’s unlikely to be the inspiration for a hit crime series in itself, despite occasional appearances in the CSI: franchise, among others. Indeed, having originally pitched this story to a well-known publication, it was judged “too gruesome for our readers.” Strap in.
Despite its ostensibly grim nature, forensic entomology is fascinating stuff, and requires practitioners to be first and foremost great entomologists. If your identification or application of insect behavioural knowledge doesn’t stack up in court, you’re more than open to both professional embarrassment and, potentially, the guilty getting off.
Fortunately, in a case recently detailed in the journal Insects, that didn’t happen. In fact, proving the manner in which clothes moths feed on human hair after death helped send a murderer who had killed in both southern Italy and England away for life.
Hair fetish or hair feeders?
Although forensic entomology has been studied since the late 19th century, and first used in securing a criminal conviction in a famous case in 1935, it is still regularly considered a ‘weak spot’ for defence lawyers to attack.
In the murder trial in question, though, rather than trying to play down entomological findings, the accused’s defence lawyer thought insects might be helpful to their arguments. They suggested that rather than the killer cutting off victims’ hair as part of a ritual driven by a ‘hair fetish’, the severing was the work of hungry bugs.
Insects considered stored product pests do like to feed on natural fibres, including clothes moths of the family Tineidae and carpet beetles (Dermestidae), and in this case, as well as distinctive ‘cut’ hair near the victim’s hand, two species of clothes moth were found at the scene where the body of a teenage girl was discovered hidden in Italy.
Microscopy settles matter, defence collapses
The moths, as it turned out, were not guilty.
Lab tests were set up to compare hairs subjected to sharp force trauma using scissors, and gnawed by the common clothes moth (Tineola bisselliella), using electron microscopy. Clear differences were observed between the two, with hair cut by sharp force exhibiting lesions with regular edges, and moth-eaten hair having concave lesions. It was the former, not the latter, which were at the crime scene, ruling out insect involvement in this respect, if not the decomposition of the body.
The killing in Italy was linked with the murder of another woman in England, found with ritualistically-cut hair in her hands. As part of a meticulous case, including evidence of the accused’s fetishism and their presence in both places where and when the crimes were committed, the efforts to establish exactly what moth feeding on human hair looks like proved valuable in securing a conviction. It’s also worth mentioning that more traditional use of insect evidence, in the form of the life cycles of dead specimens found at the scene corresponding with the period when the victim went missing, was also pivotal.
With its place in the judicial record now assured, such analysis is yet another tool at the disposal of CSI: Entomology’s professionals. It’s somewhat comforting to note that as well as playing a vital role in ensuring the streets aren’t full of dung and dead things, insects are inadvertent crime-fighters. For all the gross-out potential, bugs are going to nibble what they’re going to nibble — and we should all be very thankful for that.