We swat them, ignore them and hoover them up but the smallest creatures around us are helping forensic scientists uncover clues, link suspects to scenes and expose stories we can’t see
They might be the last thing anyone wants to find in their home, but bed bugs could soon become one of the strangest tools in modern forensics.
New research suggests the blood-sucking critters may retain usable traces of human DNA long after biting their host, a finding that could open up unexpected new ways of linking people to places and events and could help to solve crimes.
Led by entomologist Associate Professor Dr Abdul Hafiz Ab Majid and postdoctoral researcher Lim Li, a team at The Science University of Malaysia spent a decade studying the role of the insects.
Dr Hafz says: “We call bed bugs the ‘musuh dalam selimut’ [Malay for the enemy in the blanket]. They can also be spies to help solve crimes.”
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The team discovered that a common tropical bed bug species can retain human DNA in its gut for up to 45 days after feeding. In some cases this was enough to identify the hair, skin and eye colour of an individual. Though this evidence isn’t yet admissible in court, before long, police investigators hope to piece together the full profile of an offender, if the bugs – which remain hidden in soft furnishings – are present at a crime scene, acting like unexpected witnesses.
And they are not the only insects to play a role at crime scenes. Forensic anthropologist Annie Robinson, says insects are often an important detection tool. She explains: “Insects are actually at most crime scenes.”
They can even find their way into sealed crime scenes – making them perfect hidden detectives. Here, we look at the role insects and even household pets play at a crime scene.
MOSQUITOES
We may regard mosquitoes as an itchy nuisance, but in forensics, their most annoying habit can make them into unexpected carriers of evidence.
When a mosquito feeds, it draws blood directly from its prey and stores it inside its tiny body, where it can remain for long enough for scientists to analyse it, as advances in testing mean investigators need only a minuscule amount of biological material to attempt a DNA profile.
“We only need such a small amount of DNA now to get a match, and even though the mosquitoes are absolutely tiny, they can store enough,” says Annie.
MAGGOTS
Maggots have long been used in investigations – providing some of the most reliable clues investigators have when trying to understand when death occurred.
Insects can arrive within minutes of a death. Flies are drawn to decomposing bodies with remarkable speed, and once eggs are laid and hatch, the resulting maggots begin feeding, growing and developing in predictable stages. By studying which insects are present and how far along they are in their life cycle, forensic specialists can work backwards to estimate the time of death. “The most important thing insects give us, especially flies and maggots, is a really good estimation of the time of death, which we call the post mortem interval,” Annie explains.
One of the most famous cases involving maggots was the 1935 ‘Jigsaw Murders’ in Scotland. After Dr Buck Ruxton murdered his wife and a housemaid and hid their bodies, forensic entomology was used when the remains were discovered. The age of bluebottle maggots on the bodies helped establish a timeline, proving the victims had been there for weeks and playing a crucial role in dismantling Ruxton’s alibi – securing a conviction long before DNA testing existed.
Today, maggots can still play a vital role in solving crimes, acting as one of the most powerful biological clocks available to investigators..“The forensic entomologist would usually work with the pathologist, when they are trying to determine the time of death. That’s when the entomologist will come in, analyse the insects and then help with that process,” says Annie.
INSECTS FOUND IN A CAR
When vehicles travel long distances, insects often collide with bumpers, radiators or windscreens. Those remains can later be analysed to identify species native to specific regions. “Different insects are found in different locations, depending on what insects are found in the body,” says Annie. “You can also tell that bodies have been moved.”
This proved crucial in a 2003 US case involving Vincent Brothers, who claimed his rental car had remained near an airport while he was away, after flying from California to Ohio to establish an alibi. But insect remains found on the vehicle told a different story.
Entomologist Dr Lynn Kimsey examined the radiator and air filter on the car and found species that suggested it had travelled across multiple regions. Alongside odometer readings, the evidence helped demonstrate the vehicle had been driven hundreds of miles, showing just how vital insect analysis can be.
To the untrained eye, insect remains might look like dirt. But to forensic specialists, they can act as silent witnesses – recording journeys, locations and movement without anyone realising.
DOMESTIC PETS
Insects aren’t the only unexpected helpers in forensics. Animals can also play a role – even those we live alongside every day. In many cases, they don’t need to do much at all. Simply sharing the same spaces as humans can be enough. If you have pets, you probably have a love-hate relationship with their fur. It’s not great for washing machines, but it’s very useful for forensic scientists.
“That’s the Lockhart’s principle,” says Annie. “Every contact leaves a trace and that is the fundamentals of forensics. For example, I’ve got a dog and my clothes might be covered in dog hair, then I might go somewhere else and leave my dog hairs there. Someone else picks them up and by the night time they’ll be in someone else’s house that has never met my dog before – it’s easily transferable.”
That principle was put to the test in Canada during the investigation into the murder of Shirley Duguay in 1994. Police discovered a jacket stained with blood and covered in more than two dozen white cat hairs. Investigators later noticed the deceased’s estranged husband owned a white cat.
After taking a DNA sample from the cat, Snowball, scientists found it matched the hairs on the jacket. The evidence played a crucial role in convicting Douglas Beamish, marking the world’s first use of non-human DNA in a criminal court case – proving that evidence can come from our animals.
HOUSE PETS
Some animals don’t leave physical traces, but behavioural ones. In a Michigan murder case involving Martin Duram, an African grey parrot called Bud began repeatedly shouting phrases believed to echo its owner’s final moments. The case was initially believed to be a murder-suicide, but Bud’s words helped investigators identify Glenna Duram, his ex-wife, as a suspect – later leading to her conviction for first-degree murder.
While the parrot was never used as evidence in court, prosecutors considered using recordings of Bud’s speech before dismissing the idea. Unlike DNA, animal behaviour cannot be measured in the same way, but it can still help form part of the wider picture.
But the evidence is clear that insects and pets make formidable hidden detectives.
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