Crime Library: Criminal Minds and Methods

Kevin Neal, Convicted of Murder by Forensic Entomology

Enter the Cheese Skipper

The Cheese Skipper fly, Piophila foveolata
The Cheese Skipper fly, Piophila foveolata

One additional species of fly, Piophila foveolata, helped Haskell determine an approximate date of death for the two children. Known by its common name, the cheese skipper fly, Piophilidae prefers carrion in a significantly decayed form.

"Unlike the blow flies, which come in very, very quickly, the cheese skipper is one that likes more advanced decomposition," Haskell testified. "They like it when it's goopy and yucky and in a putrefaction state or beyond, in a liquefaction stage."

When he examined the tissue samples and the body bag soil, Haskell found "literally hundreds" of skipper larvae in the third instar — the final — larval stage. Using the Accumulated Degree Day method, he knew that to find larvae at that stage on September 6, 1997, meant that the adult skippers had to have visited the corpses between 45 and 90 days prior. That put the cheese skipper oviposition at July 23, 1997 at the latest.

Selvaggio wanted to remind the jury of the skipper's preferred carrion.

"Is it possible, based on your finding of the specimens on that frozen tissue sample, that a body could have ....started its decomposition on July 23?"

"No," Haskell replied. "Because the cheese skipper needs a more advanced decomposition."

"How much time would these skippers need?" Selvaggio asked.

"A minimum of a week, usually more." Haskell replied. "It could be two or three weeks."


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