Call it CSI: Abracadabra. A camera is invented which is used to find out the blood strained even when is not visible this will be helpful for the crime branch to identify the truth behind the scene. The prototype camera, developed by Stephen Morgan, Michael Myrick and colleagues at the University of South Carolina in Columbia, can detect blood stains even when the sample has been diluted to one part per 100.
At present, blood stains are detected using the chemical luminal, which is sprayed around the crime scene and reacts with the iron in any blood present to emit a blue glow that can be seen in the dark. However, luminal is toxic, can dilute blood samples to a level at which DNA is difficult to recover, and can smear blood spatter patterns that forensic experts use to help determine how the victim died. Luminal can also react with substances like bleach, rust, fizzy drink and coffee, causing it to produce false positives.
The camera, in distinction, can distinguish between blood and all four of these substances, and could be used to spot stains that require further chemical analysis without interfering with the sample.
To take an image of a scene, the camera beams pulses of infrared light onto a surface and detects the infrared that is reflected back off it. A transparent, 8-micrometre-thick layer of the protein albumin placed in front of the detector acts as a filter, making a dilute blood stain show up against its surroundings by filtering out wavelengths that aren't characteristic of blood proteins.
By modifying the chemical used for the filter, it should be possible to detect contrasts between a surface and any type of stain, says Morgan. "With the appropriate filter, it should be possible to detect [sweat and lipids] in fingerprints that are not visible to the naked eye," he says. "In the same way you could also detect drugs on a surface, or trace explosives."
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