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Out, Damned Spot: Blood-Spatter Forensics’ Newest Advance

Crime scenes spattered with blood are standard fare on Dexter, but scientists are just now working out things you may have thought were basic–like how to tell the height from which blood fell. How two physicists made a forensics breakthrough using dish soap, hot sauce, and a pair of wooden boards.

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ketchup splat

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Blood spatters are telltale marks of violent crimes, and have captured the public imagination in shows like Dexter, CSI, and Bones–shows whose cool tech may be less based in reality than special effect. For instance, it’s only just now been worked out how to determine the height from which blood droplets fell. And it didn’t take anything high tech–just a couple of guys in a lab (namely Fred Gittes and Chris Varney from Washington State University) armed with a hinged “clapper” to send the blood flying.

Crime scene investigators have long been able to tell where a blood spatter came from, because elliptical splashes are a dead giveaway. But when the source of the blood has been moved–say, from a sitting to a lying-down position–the analysis can reveal details of the crime itself. This can be critical information because in a complicated court case it could help to know if the victim was sitting, standing, or already on the ground–the data plays into arguments about self defense and other technicalities.

Gittes and Varney performed experiments by scattering “blood” made from Ashanti chicken wing sauce and Ivory dishwashing soap, and then trying to model the behavior. It turns out that a good deal of the math was surprisingly basic, and they came up with a model for working out how high a blood droplet fell from. Their method prevents investigators from drawing the wrong conclusions, because the algorithm self-corrects (the graphs deviate from straight lines if the analysis is wrong.)

Sometimes an important innovation doesn’t require a supercomputer or rocket science–just some brainpower, elbow grease, and wing sauce.

[Image: Flickr user clovenhoof]

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About the author

I'm covering the science/tech/generally-exciting-and-innovative beat for Fast Company. Follow me on Twitter, or Google+ and you'll hear tons of interesting stuff, I promise. I've also got a PhD, and worked in such roles as professional scientist and theater technician...thankfully avoiding jobs like bodyguard and chicken shed-cleaner (bonus points if you get that reference!)

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