A Jury of Bugs: The Flaws of Forensic Entomology

Climate change and a reliance on DNA for species identification may be reducing the ability of forensic entomologists to solve crimes.

Best known for inferring times of death from the developmental stage of maggots in corpses, the skills of forensic entomologists take many forms: based on bugs picked from a car's windshield, the lead character in this story recently told a jury that an accused murder had, contrary to his alibi, driven west of St. Louis. The man was later convicted.

However, the maps used in the case plotted out clearly-defined borders for species range, when the real borders are far more hazy. And that's not the only problem: species maps are often out-of-date, bugs regularly hitch long-distance rides on cars and trains, and climate change is radically changing species distribution.

Misidentification of insects can also lead forensic scientists astray, says Kimsey. At a recent North American Forensic Entomology meeting she assembled six blowfly specimens and asked attendees to identify them.
"No one identified them all correctly," says Kimsey. "We were very discouraged. If you can't identify the blowfly correctly, then your estimation of the postmortem interval could be wrong."

Fewer young entomologists are interested in using classical morphology to identify species, Kimsey says, preferring modern molecular techniques based on DNA sequencing. But genetic sequencing will be of limited use for cases such as hers, she says. Most insects don't appear in genetic databases because their genes have not yet been sequenced.

Maybe I just haven't seen the right episodes, but wouldn't it be nice if CSI did a show on just how unclear forensic technologies can sometimes be?

The tell-tale grasshopper [News@Nature]

Image: University of Florida*