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Sniffing a rat in a bag of ruined chips: how forensic scientists tell contamination from tampering.

Some crime scenes are exactly the size of a bread box.

Every year forensic scientist Brendan Nytes sees a few cases where a dead rat or mouse is found in a box of cereal, a jug of vinegar or a loaf of marble rye. His job is to collect evidence that can help distinguish genuine contamination from the surprising number of cases involving the intentional introduction of a dead rodent to a perfectly wholesome food product.

While critters do make their way into food accidentally, many arrive with outside help, said Nytes, a microscopist with Microtrace, a private forensic lab based in Elgin, Ill. A careful postmortem may lead investigators to a litigious consumer, vengeful employee or maybe just a kid who is willing to take a prank a little too far.

When a product containing a dead animal arrives at the lab, Nytes reported February 26, he and his colleagues first scrutinize the crime scene. Gnaw marks on the inside or outside of the container may reveal a point of entry or an attempt to escape. Feces or urine within the container can indicate whether the animal arrived in its tomb alive.

But it's a necropsy--the animal version of an autopsy--that can most readily rule out death by food processing.

Ligature marks on the neck? Probably died in a mousetrap. Analyzing stomach contents can reveal the green dye used to mark rat poison or a completely empty belly, both suspicious if the rodent supposedly expired in a box of food.

When faced with mere bones or fur scraps, scientists must first ascertain what animal they are dealing with. Some body parts allow for a much quicker ID than others, said forensic morphologist Bonnie Yates of the U.S. Fish and Wildlife Service Forensics Laboratory in Ashland, Ore.

"Teeth are great because that's how animals make their living," said Yates. "Tail or rib bones, not so much. But if you have a remnant of original form, chances are if you have someone who knows their way around a carcass, they will know what it is."

Occasionally there isn't a carcass at all. Nytes has seen cases where package contents really settled during shipping--so much that a consumer misidentifies a misshapen mass of oats and starch as a body part.

"This is actually a big deal--a consumer often claims it's a rodent, and it isn't," Nytes observed. "It's a rock of product."

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Title Annotation:Science & Society
Author:Ehrenberg, Rachel
Publication:Science News
Geographic Code:1USA
Date:Mar 26, 2011
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