Blood spatter 3D model to make crime scene investigation easier

July 21st, 2010 - 2:25 pm ICT by ANI  

London, July 21 (ANI): Reconstructing the course of events leading up to a murder could become easier and more accurate, thanks to a new system for making a high-resolution 3D map of a crime scene.

Scientists have developed a system that more realistically reconstructs the ballistics of blood droplets at a crime scene.

Bloodstain pattern analysis involves studying blood spatters on walls, floors and furniture, using the length and width of elliptical stains to estimate their angle of impact.

However, the method of testing this is both time-consuming and prone to error: a spatter of blood does not travel in a straight line as the strings suggest, but follows a ballistic curve that depends on its velocity.

So, Ursula Buck and colleagues Silvio Nather and Beat Kneubuehl at the University of Bern have made the new model.

The first step is to use a laser scanner to make a 3D digital map of every object in the crime scene. This does not include much surface detail, so the team also uses a digital camera to capture the shape of bloodstains.

They then use another laser ranging device called a tachymeter to obtain a precise location for each blood spot in the 3D model.

Next, they calculate the mass of each drop from the size of its stain, and use this to calculate its maximum potential velocity - air drag would rip apart a droplet if it travelled faster than this limit.

With that information, and an angle of impact estimated from the shape of the stain, their software projects a realistic trajectory backwards in time to locate the origin of the blood spatter.

“The 3D results give us good clues about the area of origin, the number of blows, the positioning of the victim and the sequence of events,” New Scientist quoted Buck as saying. (ANI)

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