How to Detect Fingerprints and Blood at a Crime Scene

There are many field tests available for testing the six forms of evidence: blood, narcotics, impressions, fingerprints, trace, and firearms and ammunition (CTU, 2006). Today, I want to focus on the reagent tests that are available for fingerprints and blood I have chosen these two types of reagent tests because they are the most common form and usually the most important pieces of evidence collected at a crime scene.

What is a reagent? A reagent, by definition, is "a chemical agent for use in chemical reactions" (Reagent, 2001). There are several forms of reagent tests that can be performed to develop fingerprints that are not visible to the naked eye. There are several reagents that are used to develop fingerprints at the crime scene. The following is a list and description of the various reagent tests available for fingerprints.

Ø Amido Black - dye that stains the protein found in blood and causes a blue-black reaction and should only be utilized to enhance blood-contaminated prints. This test should only be performed on non-porous materials. All blood samples should be obtained prior to utilizing Amido Black as it can destroy body fluid evidence (Warrington, 2005).

Ø Crazy glue (cyanaoacrylate) - easily lifts prints from surfaces such as cars, guns, and bullet casings. Should be used when brushing for prints would alter or destroy prints (Smith, 2006). Photographs should always be taken prior to using crazy glue (Smith).

Ø Ninhyndrin - is a chemical that bonds with the amino acids in fingerprints and will produce a blue or purple color (Smith). It is used to lift prints from surfaces such as paper and cardboard. Photographs should be taken to document the prints (Warrington).