Research reveals that insects preserve human DNA for up to 45 days, allowing police to trace the genetic profile and identify physical characteristics of suspects present at the crime scene
From domestic pest to police tool: scientists have managed to transform bedbugs, feared for their infestations and bites, into tiny allies to solve crimes. In a laboratory lit by white lights, a research assistant places a container of bedbugs on his forearm that, through a mesh, feed on his blood, all in the name of science.
A team of researchers from the University of Science Malaysia (USM) discovered that tropical bedbugs are capable of preserving human DNA for up to 45 days after they have fed on its blood. These tiny creatures, which love to hide in the seams of mattresses and pillow covers, can become key evidence of the presence of possible suspects at a crime scene.
From a single drop of blood, the police could establish the complete profile of an attacker, he explains to AFP o entomologist Abdul Hafiz Ab Majid. “Chamamos os percevejos de ‘enemies in blankets’ [‘inimigo no cobertor’, em malaio]. But they can also be spies” to help solve crimes, he points out.
Eye color
In a laboratory at USM’s School of Biological Sciences, Hafiz and postdoctoral researcher Lim Li spent nearly five years studying the tropical stink bugs Cimex hemipterus. There, they raise these insects in simple containers, each wrapped in black plastic to mimic the conditions in which they thrive. Insects absorb between 1.5 and 5.3 microliters of blood in each “meal”, “an amount smaller than a drop”, highlights Hafiz.
The researchers found that DNA extracted from bed bugs fed on human blood allowed them to recover a basic “phenotypic profile” — a person’s visible characteristics — as well as determine sex up to 45 days later. Researchers can determine the sex, eye and hair color, and skin tone of potential suspects long after they have left the crime scene. To do this, they use STR (short tandem repeats) and SNP (single nucleotide polymorphisms) markers, specific DNA sequences extracted from blood.
The USM study was published in the scientific journal Nature two years ago. It was the first documented use of tropical bedbugs for forensic purposes.
Perfect expert tool
Unlike mosquitoes and flies, bedbugs can’t fly, and once they eat, “they swell up and can’t move as much anymore,” says Hafiz. Furthermore, they can only move within a radius of around six meters from the place where they feed.
“This is what makes them unique. We can say that they are perfect to be used as a forensic tool, unlike mosquitoes that fly away”, he adds.
Back at the laboratory, Lim tests his own blood and jokingly claims to be a “willing victim” in the name of science. “I allowed [aos percevejos] feed on my blood to see how long it took for human DNA to disappear”, he explains.
For Lim, these inconspicuous insects are “misunderstood creatures” that do not transmit disease, although their bites cause a rash that can be bothersome for weeks.
Researchers imagine a future in which tiny bedbugs found at crime scenes could help identify murder suspects, but Hafiz cautions that this is not a silver bullet. “Bedbugs have their limits, especially when it comes to resolving old cases,” he noted. “They only offer investigators 45 days to use them as evidence, and only if they are present at the scene of the crime.”
*With information from AFP
Published by Nícolas Robert
