Criminal Scene Investigation

Posted onDecember 27, 2011 - 7:27 pm by Admin | 0 Comments

A wide variety of biological and chemical evidence can be left at a crime scene and it is up to investigators to determine what is relevant. Many of the tests they use involve chemical reactions or the use of instrumentation back at the laboratory. Tests for blood, fingerprints and the criminal use of drugs utilize these tests when connecting them back to a crime.

Luminol Shows Investigators the Way

An important tool in detecting biological evidence at a crime scene is luminol (5–amino–2,3–dihydro–1,4–phthalazine-dione). This chemi-luminescent compound gives off blue greenish light when it reacts with metal ions. Iron is stored in the protein called hemoglobin, a component of red blood cells and reacts with luminol. The metallic element acts as a catalyst when it comes in contact with a luminol mixture causing an oxidation reaction.

Normally, Investigators prepare the luminol solution by mixing luminol powder with hydrogen peroxide and other chemicals. Luminol also reacts with other substances like rust or saliva so more tests are needed to positively determine the presence of blood. Since luminol changes compounds it reacts with, original samples of suspicious substances are collected prior to luminol contamination, for further testing to identify the substance.


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