General Question

lanahopple's avatar

Is there a specific name for the chemistry that is used in the detection of fingerprints?

Asked by lanahopple (455points) February 22nd, 2010
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5 Answers

bostonbeliever's avatar

forensics, lol
but seriously:
scroll down to “methods of fingerprint detection”

ETpro's avatar

It depends on the type of fingerprint and the substrate material it is on. At violent crime scenes, there are often prints left by blood or other materials on the perpetrator’s hands. These can simply be photographed. Chemistry comes into play for latent prints made solely by the moisture and oils in the perpetrator’s skin. The forensics experts will select a “developer” reagent to render these faint prints more sticky, then dust them with a powder that adheres to the sticky spots where the traction ridges of the fingertip/s actually contacted the substrate. They them photograph the resulting print.

The exact chemistry chosen for the developer and powder depend on what sort of material the print is on.

marinelife's avatar

“The cyanoacrylate fuming method (often called the super glue method) of developing latent fingerprints has proven to be an effective tool for professional investigators, and the quality of its results has made it a popular one. Any agency that works with latent fingerprints and does not already use the cyanoacrylate fuming method should seriously consider adopting it.

The basic concept behind all of the chemical techniques is to apply something that will chemically react with one of the constituent chemicals of latent fingerprints to the area suspected of containing such a fingerprint. The resulting reaction will give all present latent fingerprints a new chemical composition. This new chemical composition will make the latent fingerprints easily rendered visible, and they can then be photographed.

The super glue method is no exception to this rule. Most liquid super glues are really either methylcyanoacrylate or ethylcyanoacrylate. Less common types of super glue include butylcyanoacrylate and isobutylcyanoacrylate. Fortunately, all these types of super glue are nearly identical physically and chemically. Super glue reacts with the traces of amino acids, fatty acids, and proteins in the latent fingerprint and the moisture in the air to produce a visible, sticky white material that forms along the ridges of the fingerprint. The final result is an image of the entire latent fingerprint. This image can be photographed directly, or after further enhancement.

To enable such a reaction to take place, the cyanoacrylate must be in its gaseous form. The basic procedure to develop latent fingerprints using super glue takes this fact into account, but is still not overly complicated. The surfaces that are to be checked for latent fingerprints are placed in an airtight tank along with a small heater. A few drops of liquid super glue are placed into a tiny, open container, and the container is placed on top of the heater inside the tank. The tank is then carefully sealed, and the heater activated. According to Lee and Gaensslen, the boiling point for most super glue varies between forty-nine and sixty-five degrees celcius (roughly one-hundred twenty to one-hundred fifty degrees fahrenheit) depending upon its exact chemical composition1.

Once the super glue in the container reaches its boiling point, it will begin to boil away into the surrounding atmosphere, creating a concentration of gaseous cyanoacrylate. If any latent fingerprints exist anywhere inside the tank, they will eventually be exposed to the gaseous cyanoacrylate. This exposure and the natural humidity contained in the atmosphere are enough to trigger the reaction automatically. Thus, once everything has been set up, the investigator merely waits for the reaction to occur. The whole reaction can take over two hours, with the exact time determined by the size of the tank, the concentration of the gaseous cyanoacrylate in the air, the humidity of the air, and numerous other factors.”


lilikoi's avatar

forensic science

lanahopple's avatar

ya I went to a web site and it called the specific chemistry, Dactylography, but i’m not sure that is right.

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