January 18, 2019 - Author: Joy Landis, MSU Entomology
There’s an unsolved crime: a body found in a lake with little algal growth and no evidence of insects. Extremely odd, as other evidence suggests the body may have been in the water for as long as 21 days. Oxygen Network’s Smiley Face Killers: The Hunt for Justice series thinks it’s strange, too, and strange is their business.
In an attempt to solve the cold case for an episode of their series, investigators and the show’s producers contacted Michigan State University entomology professor and forensic entomologist Eric Benbow. He’s an expert on aquatic decomposition and carrion ecology, including developing translational ways to use insects and microbes in death investigations. Last summer, they filmed Benbow in the lab with his students and brought him to the site of the crime.
“They took me to the lake and showed me the evidence collected: clothing, photos, autopsy report,” said Benbow. “I called around to colleagues and we all agreed the lack of insect evidence was peculiar. If the body’s been in water for nearly three weeks, everything we know indicates it should be colonized by aquatic insects. When the body floated, it should have been colonized by terrestrial insects, unless the body only floated for a day or so. Then maybe you don’t see mature insects, but you should probably see eggs or larvae (maggots).”
Benbow didn’t have answers for investigators, but offered to test the conditions to learn more about microbial growth on the body and shirt fabric and what may have occurred with the aquatic conditions and insects. The microbial studies characterized when certain microbes colonized and how their communities developed over decomposition. With this information, researchers can create a “microbial clock,” an indicator of the passage of time, in this case how long the body was submerged in water.
The methods for the research were somewhat gruesome, which Benbow’s forensic team is used to. They collected several large pig carcasses, dressed them in clothes and submerged them in a pond. Then they visited every other day for 21 days (about the amount of time the crime victim was missing), swabbing the carcasses and clothes for microbes and identifying which aquatic and terrestrial insects showed up and when.
“Typically, there are some aquatic insects who don’t feed on the carcass but make habitat on the clothing or body and those were the ones we were looking for,” Benbow said.
Using three replicates of the experiment with two untouched pig carcasses as controls, the concept was to come as close as possible to replicating the crime scene. The pond available for the research was smaller and shallower than the lake. The body was found in a shallower area of the lake, however, it is possible that the decedent drowned, the body sank to the deeper, colder and low-oxygen water and later floated to the shallow area.
There were no insects reported in the autopsy report and none visible in photos taken at the crime scene. When Benbow’s team ran their experiment, they found all kinds of insects occupying the carcasses within a day or two.
“The lack of insects in the reports is highly unusual and therefore suspect. I don’t know if the medical examiner found insects, but did not report them, but I did examine the photos and couldn’t see any evidence of insects or eggs in them,” Benbow said. “We will be submitting our findings to the district attorney. Meanwhile our research will be published in journals where the scientific community can evaluate and build on it.
Benbow is intrigued to see where everything goes. Hopefully, an unsolved crime can be solved.