Forensic science is always interesting to students. The mystery and puzzle solving are hard to resist. Here’s a real case you can use to get students thinking scientifically while integrating knowledge of insect life cycles—a timely topic for spring. The NYtimes.com reports how the unsolved cause of death of a woman in Las Vegas was solved based on insect life cycles in this story, The Truth, Revealed by Bugs: The Case of Brookey Lee West.

The graphic from the National Institutes of Health (credited to the Cleveland Museum of Natural History), illustrates how the blow fly is a natural clock telling the time of death, since they lay eggs in a body within 24 hours of the body’s death. In this case, no blow flies were found, indicating that either the time of death was during a season when blow flies are absent or that the person was still alive when they were shoved into a trash can in a storage garage. This evidence and subsequent inference contradicted the victim’s daughter’s story regarding the death. This contradiction then led to suspicion that the daughter was guilty of murder.

While no blow flies were found, scuttle flies were. See Decomposition: What Happens to the Body After Death for details on this insect’s life cycle and behavior as related to solving murder mysteries.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Here we connect to two National Science Education Standards domains: Life Science and Science as Inquiry. Present the scenario to students as perhaps hypothetical. Friends and neighbors of a woman in Las Vegas notice that they have not seen her much recently. Her daughter tells them her mother has gone to California to stay with the woman’s son. Some people wondered if there was more to this story, since it was known that the mother was an alcoholic and the daughter and mother did not always get along.

Some three years later, the woman’s body is found stuffed in a garbage can in a storage unit in Las Vegas. Upon this discovery the daughter admits to putting the body there after her mother died of natural causes and she panicked, she didn’t know what else to do.

Ask students if there is any way to determine if the daughter is telling the truth. They’ll have some creative ideas including a lie detector test or administering a truth serum. Students could be asked to research those for their reliability.

Ask students if they know what happens to a body in nature. What happens when a deer or raccoon dies? Do they suppose there are any patterns in body decomposition? Such as? They might mention dehydration or bacteria or fungal growth and activity. Are there more easily observed organisms that move in? With enough cues, they should be able to mention flies. What do flies do then? Why are they attracted to the body? They lay eggs, reproduce. You could review a generalized insect life cycle with students. See this page from University of Wisconsin Entomology department for a nice graphic and written explanation: http://manduca.entomology.wisc.edu/about/lifecycle.html.

So what would the environmental conditions have to be to allow for the flies to move in? Well it wouldn’t be below freezing out, and they would need access to the body. Is there only one species of fly? No. Have them collect information on the two species mentioned here, the blow fly and the scuttle fly. The NIH page, Visible Proof: Technologies contains an informative slide show specific to blow flies and forensics. The Australian Museum has a nice page on scuttle flies, http://www.deathonline.net/decomposition/corpse_fauna/flies/coffin.htm.

Finally, tell them that when the body was examined, there was no evidence of blow flies, however scuttle flies were found. What could be inferred regarding season of and/or place of death? Was the daughter telling the truth regarding a natural cause of death? How do they know?

The following are some related resources from the National Science Digital Library Middle School Portal: Forensic Science Under the Microscope; Animals of the World (click on “insects and arachnids”); and Science Sampler: Forensic Metrics.

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