How Do Crime Scene Investigators Really Collect Fingerprints?

If you watch CSI on TV, you may be convinced that collecting fingerprints involves dusting them with a white powder and calling it a day. While this can be accurate in some scenarios, there are other methods used to collect fingerprints in real life.

Porous Surfaces

When real crime scene investigators are collecting fingerprints, they have to use different techniques for different textures. For porous surfaces, like paper, the method is actually fairly well-represented by the TV show. The substances on the skin, usually mostly water, will be absorbed by porous surfaces, and dust will stick to it. This allows the investigator to either lift the print by using a clear tape to pick up the dust pattern or to take photos.

Non-Porous Surfaces

For surfaces that aren’t porous, like glass or plastic, dusting doesn’t work and can actually destroy the fingerprints left behind. In fact, these fingerprints can be destroyed so easily that investigators have to make certain not to touch them. They instead will carefully package up the item so that they can later be examined with specialized lights.

What Happens next?

Once investigators have collected fingerprints, they can be examined and, ususlly using a computer program, they can be compared to other fingerprints to connect people to crime scenes or objects. Fingerprints are actually more unique than DNA, and even identical twins with similar DNA will still have different fingerprints. You can learn all about the process at the CSI educational exhibit in Las Vegas.


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