In 1668, Francesco Redi reported on his experiments with rotten meat. His work proved that maggots did not spontaneously appear, they required flies to lay eggs on the meat. These eggs hatched into maggots, and the maggots pupated into flies (Britannica, 2023). Considering that scientists learned that flies grow out of maggots in the 17th Century, you’d think that Forensic Entomology was an equally young science. However, the first murder case solved by flies was in China, in AD1235. Even then, people understood that blowflies are attracted by the smell of corpses, which they can detect from up to 10 miles (16 km) away (Osterloff). They and their larvae are the most common of the Crime-solving insects used in Forensic Entomology.
Defining Forensic Entomology
If forensic science is the application of the scientific method to subjects investigated by a court of law, then forensic Entomology is the study of arthropods and insects, and their associations to cases subject to a court of law. In brief, Forensic Entomology uses insects to solve crimes.
What does a Forensic Entomologist do?
The forensic entomologist is responsible for estimating how long it was since the time of death, or the Post-mortem Interval (PMI). After about 72 hours, the usual signs of time passing since the point of death, such as rigor mortis, have faded away. At this point, the police call in the forensic entomologist, who studies the life cycle of the insects that have colonised the corpse.
Sometimes, Crime Scene Investigators (CSIs) collect the insects and send them to the forensic entomologist. However, the entomologist finds it helpful to visit the scene for themselves. This way the scientist can prove the evidence was correctly collected for admissibility in court. Also, CSIs with their generalist rather than specialist knowledge, might miss the oldest specimens or pupae that have buried themselves for metamorphosis (McDermid, 2014).
The insect life cycle is predictable. Maybe, environmental conditions, such as the temperature or whether a body was buried, can affect the process, but it is possible to compensation for these factors (Crime Museum, 2022). And this is where the forensic entomologist is king.
Waves of Crime-solving Insects
The reason insects are so useful in estimating the time since death is that different species colonise the body at different periods of the decay process.
Flies
Credit: https://commons.wikimedia.org/wiki/File:Esperimento_abiogenesi.jpg
The first flies to show up are the blowflies. As I mentioned in the introduction, they can smell a dead body from miles away. As an indicator of the time since death, blow flies are one of the best. In as little as ten minutes, they can be detected. A female fly will lay her eggs, usually around openings such as the nostrils, or any open wound. Within 24 hours, these eggs hatch into maggots as seen in Image 2, a modern reconstruction of Francesco Redi’s experiment with rotten meat. The predictable timings of their life cycle, from egg to larvae to pupae, allow a forensic entomologist to estimate how long a body has lain there. Another early arrival at the scene is the flesh fly. Instead of eggs, these flies lay live young.
Later arrivals, such as the house fly, only arrive when the body decomposition arrives at bloating. And a cheese fly will wait 3 – 6 months before arriving (The Forensics Library ).
Not just flies
Beetles are also scavengers attracted to the corpse. Later arrivals include moths, which feed on the hair of the deceased, and various species of mites. Ants and Wasps will arrive at the crime scene, not for the corpse, but because they are predators and the profusion of their prey attracts them. A forensic entomologist knows the life cycles of all these arthropods and uses them as a reliable indicator of the PMI (The Forensics Library ).
Factors that influence the life cycle of Crime-Solving insects
The life cycle of the blowfly is typically 15 days from newly laid egg to adult fly. The egg is laid and one day later hatches. For four days, the maggot does nothing but eat, growing from 2mm to 20mm. This old maggot then finds a dark space that will protect it from scavengers such as birds or predatory wasps. This can be burrowing into the ground or, if inside then cracks between the floorboards are a welcome hiding place for a pupa to form. After around ten days the pupa hatches into an adult fly (McDermid, 2014).
If it was always this easy, then the courts wouldn’t need experts. A statement like “a blowfly takes 15 days to mature” is true at the height of summer in the UK. Ambient temperature is a major factor in the development of cold-blooded creatures, such as insects. Warmer temperatures speed up growth, while cooler ones slow it down. Indoors versus in the woods, must be taken into account. Drugs, such as heroin and morphine also affect a fly’s development (The Forensics Library ).
Did the murderer wrap the body, thus preventing access to the insects? In experiments at the Natural History Museum in London, UK, entomologists have discovered that flies can lay their eggs through the zip of the suitcase. But the container prevented the arrival of the flies by about 3 days (Hall, 2015).
Every possible influence must be accounted for, or a judge can throw the evidence of the forensic entomologist out of court (The Forensics Library ).
Case Studies of Forensic Entomology
Case Study 1—The Ruxton Case
The display cases of the Natural History Museum entomology section, preserve the insects collected as part of the Ruxton Murder. It was the first murder case in modern times where the evidence from insects solved the crime.
Credit: https://commons.wikimedia.org/wiki/File:GardenholmeLinnBuckRuxtonDiscoveryMoffattSeptember1935a.jpg
In 1935, parts of two bodies were discovered in a Scottish Ravine, see Image 3. Dr Ruxton was a GP in Lancaster, UK. He became increasingly jealous of his outgoing wife and strangled her. He also killed the housemaid to prevent her from testifying to the murder. Cutting up the bodies and wrapping them in newspaper, Dr Ruxton drove over 100 miles to dispose of the evidence. Unfortunately, he accidentally knocked over a cyclist on his way home, and they took his number plate.
Unusually for the time, the detective in charge of the case collected the body parts and the maggots around them. With the predictable life-cycle of blue bottle flies, they established that the sighting of Dr Ruxton and the disposal of the bodies happened within the same time frame. Ruxton was convicted of the dual murder, because of tiny flies (Wilson).
Case Study 2—The oldest known murder solved by Insects
As I mentioned in an earlier article, the earliest printed Forensic Science Manual, The Washing Away of Wrongs, was written by Song Ci in the 13th Century. In this work, Song Ci discusses how a coroner had identified the wounds of a body as formed by a sickle. No one confessed to the murder, but the coroner learned that the victim had argued about a loan with someone in his village.
Knowing that flies are attracted to blood, the coroner insisted that everyone in the village who owned a sickle should stand on the road with their tools at their feet. Even though the murderer had washed away the blood of his victim, flies still circled his sickle, able to smell the death. The money-lender broke down and confessed at the testimony of the insects (Hall, Ed. 2010).
Case Study 3—Vincent Brothers Case
In 2003, Joanie Harper was found murdered along with her three children and her mother, in Southern California. The obvious suspect was Harper’s ex-husband, Vincent Brothers, but he was, to all appearances, in Ohio at the time of the murders, visiting his brother, Melvin. His credit card and Cell Phone were used at a time when he couldn’t possibly be murdering his wife in California.
The police focused on a rental car. The mileage at the car’s return was such that he could have driven to California from Ohio. But how would they prove it?
The air filter and the radiator of the car were sent to forensic entomologists. Caught in the grill were bits of insects. After close examination, the entomologist discovered pieces of a grasshopper that was only found in areas to the west of the Rocky Mountains. Vincent Brothers had driven the car from Ohio to California.
But what about the evidence of the phone and the credit card? Melvin Brothers finally admitted he had used the items, buying exactly what Vincent had told him to buy.
Vincent Brothers was convicted of the Massacre of his family, on the testimony of grasshopper fragments (Dziemianowicz , 2021).
Finally
Insects don’t lie. All the articles on forensic entomology make that point. It doesn’t matter how much the human witnesses talk of their innocence, the evidence of the crime-solving insects will always present investigators with the truth.
References
Britannica, T. Editors of Encyclopaedia (2023, February 25). Francesco Redi. Encyclopedia Britannica. https://www.britannica.com/biography/Francesco-Redi
Crime Museum. 2022. Forensic Entomology. Crime Museum LLC. https://www.crimemuseum.org/crime-library/forensic-investigation/forensic-entomology/
Dziemianowicz, Joe. (2021) ‘That’s a lot of Hate.’: Dead Insects Lead Detectives to Man Who Killed 5 Family Members. Oxygen True Crime. https://www.oxygen.com/family-massacre/crime-news/vincent-brothers-slaughtered-family-caught
Hall, M. (2015) Forensic Entomology, The Crime Scene. Wellcome Collection. https://www.youtube.com/watch?v=HIVKISCmjTQ
Hall, M.C. (Ed.) (2010). Washing Away of Wrongs: Song Ci. Translated by Herbert A Giles. Lulu books.
McDermid, V. (2014) Forensics: The Anatomy of Crime. Profile Books Ltd.
Osterloff, E. Murder, Maggots and Forensic Entomology. Natural History Museum. https://www.nhm.ac.uk/discover/murder-maggots-forensic-entomology.html
The Forensics Library. Forensic Entomology. https://aboutforensics.co.uk/forensic-entomology/
Wilson, S. Dr. Buck Ruxton. Murderpedia. https://murderpedia.org/male.R/r/ruxton-buck.htm
