New forensic tool: chicken wing sauce and dish soap

Using a clapper board, chicken wing sauce, dish soap and trigonometry, a physicist and his doctoral candidate have developed a formula for analysing blood spatters.

New technique for analysing blood spatters uses chicken wing sauce, dish soap and a clapper board

The new system can determine exactly where blood spatters originate – a critical piece of evidence in not only solving a crime but securing a conviction.

Up until now, forensic investigators have been able to determine the direction the blood has come from – the stain’s elliptical shape practically points to it – but the tough part has been figuring out the height of the source.

“I talked informally with a public defender and he said that’s its crucial to know the height because so often it’s a self-defence issue,” said Fred Gittes – a physicist at Washington State University. “A defendant may claim that a victim was standing rather than sitting. That’s a big deal apparently.”

Gittes and physics doctoral candidate Chris Varney began tackling the problem with a clapper – two boards on a hinge that could be clapped over the liquid – to produce a spatter from a known and measurable height and angle.

They experimented with corn syrup, food colouring and different sauces to find a liquid that created blood-like impact shapes, before settling on a blend of Ashanti chicken wing sauce and Ivory dish soap.

Working backwards from measurements of known spatters and sources, the pair found that well known equations of projectile motion could be used to develop a formula giving them the height of the liquid’s origin.

They also found that plotted on a graph, data points on specific drops form a neat line when the formula is working correctly. If the drops are launched from too wide a range of angles the method won’t work and data points won’t line up – giving investigators an idea that they might be on the wrong track.

A chance comment from a scientist with forensic training – who said crime scene investigators could do with a better way of analysing blood spatters – prompted the research.

“It seems as though what was being done was very crude from a physics point of view, and that intrigued me,” said Gittes.