Bed Bugs as Forensic Tools: How Scientists Use These Blood-Sucking Insects to Solve Crimes

In a brightly lit laboratory, a dedicated research assistant extends his arm and carefully places a mesh-topped container against his skin, allowing hungry bed bugs to feed on his blood—all for the advancement of forensic science.

These typically despised household pests have revealed an unexpected potential as crime-solving allies, according to groundbreaking research from Malaysian scientists.

Researchers at the Science University of Malaysia (USM) in Penang have discovered that tropical bed bugs can preserve human DNA for up to 45 days after feeding on someone's blood, making them valuable evidence collectors at crime scenes.

These tiny insects—which typically hide in headboards, mattress seams, and pillow covers—could potentially help investigators identify suspects through blood analysis.

From minuscule blood samples, forensic teams may eventually extract comprehensive profiles of offenders when bed bugs are present at crime scenes.

Entomologist Abdul Hafiz Ab Majid told AFP that analyzing these insects could reveal a suspect's gender, eye color, hair color, and skin tone.

"We call bed bugs the 'musuh dalam selimut' (enemy in the blanket)," Hafiz explained, noting that "they can also be spies" in criminal investigations.

Deep within USM's School of Biological Sciences, Hafiz and postdoctoral researcher Lim Li have spent nearly five years studying tropical bed bugs (Cimex hemipterus), the species most commonly found throughout Malaysia and other tropical regions.

The research team cultivates these insects in containers wrapped in black plastic to simulate their preferred dark environment.

"We place folded pieces of paper inside the small containers so the bed bugs have something to climb on," Hafiz described.

Maintaining a consistent laboratory temperature between 23-24°C, the researchers observed that each bed bug consumes between 1.5 to 5.3 microliters of blood per feeding—"an amount less than a droplet," according to Hafiz.

Their research revealed that DNA extracted from bed bugs that had consumed human blood could provide basic "phenotypic profiling"—observable physical traits—as well as gender identification for up to 45 days after feeding.

Using specialized DNA sequences called STR (Short Tandem Repeat) and SNP (Single Nucleotide Polymorphism) markers, scientists can determine gender, eye color, hair color, and skin tone of potential suspects long after they've left a crime scene.

The groundbreaking USM study, titled "Human profiling from STR and SNP analysis of tropical bed bug, Cimex hemipterus," was published in Nature's Scientific Reports two years ago, marking the first documented forensic application involving tropical bed bugs.

Unlike flying insects such as mosquitoes and flies, bed bugs remain relatively stationary, especially after feeding when they become "engorged and can't move around that much," Hafiz explained. Their limited mobility—typically within 20 feet (six meters) of their feeding location—makes them particularly valuable as forensic tools.

"That's what makes them unique. We can say they are perfect to use as a forensic tool compared to mosquitoes that... fly away," Hafiz added.

The insects prove especially useful at crime scenes where fluids have been deliberately removed to destroy evidence, as bed bugs often remain hidden and undisturbed.

In the laboratory, researcher Lim demonstrated a feeding session firsthand, describing herself as a "willing victim" for scientific advancement.

"I let them feed on my blood when I wanted to test how long (it would take) the human DNA to degrade," she explained.

Lim emphasized that these misunderstood creatures don't transmit diseases, despite leaving itchy rashes that can persist for weeks.

"Maybe we can try educating people because the bed bugs are not actually vectors. So even if you get bitten, they can't transmit diseases to you," she noted.

While the researchers envision a future where bed bugs at crime scenes could help identify perpetrators, Hafiz acknowledged their limitations.

Their forensic usefulness extends only 45 days, and they must be present at the crime scene to provide valuable evidence, limiting their application in solving cold cases.