Physicists test out their CSI skills with chicken wing sauce and dish soap

Although TV detectives can solve a crime with an eyelash and a laboratory full of lasers, real-life crime scene investigation still has some basic hurdles to get over. Recently, it leapt one with a bucket of soap.

You know the scene: an investigator ducks under yellow police tape and walks into a house humming with people in dark jackets collecting evidence. There are horrific blood splatters everywhere. The detective looks at a splotch, the camera zooms in on his eyes, and the scene flashbacks to a slightly out-of-focus shot of the victim with a lacerated arm splashing blood across the wall. The implication is that the detective can look at the blood splatter and recreate the action that caused it in his mind. In reality, the detective sometimes can't even recreate it with props and careful consideration.

That's not to say that the police don't know their business. Although the shape of the splatter lets investigators know at what angle it made contact with the wall (and lets them backtrack which direction the blood came from), they often can't be sure of the exact height of the blood-spurting wound. Recently, Washington State University physicists went to work on this height problem.

First, the WSU team used Ashanti chicken wing sauce and Ivory dish soap to get the right consistency for the test droplets. Next, they built a set of two boards that was clapped together over the test liquid and splattered the drops from a measurable height.

From there, researchers worked backwards to create equations that used the angles of the surfaces that the drops landed on, the drops' distributions, and the drops' size and shape to give correct results for the height they'd been tossed from. Additionally, the test is self-correcting. When used correctly, the data points for different drops line up when plotted on an graph. If they don't line up, the police are making the wrong conclusion (or working with unrelated drops).

This method of determining the exact height of a blood spurt could help police both catch killers and exonerate the wrongly accused. Having accurate information of the body position of each person involved in a crime could help make sense of conflicting testimonies. Or it may help TV programs have more math. Either way, it's an admirable goal.

[Via ArXiv and WSU]