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Forensic microanalysis is that area of criminology that requires instrumentation for its findings. Almost all of this phase of analysis occurs in crime labs wher it is sent for identification, comparison, or both. Identification is the process of using analytical chemistry techniques of which over 30 exist. The levels of certainty vary depending on the type of evidence, but analysis may include simple titration or be as complex as NMR. It generally takes as many as five or six tests to be able to determine to some level of certainty what the evidence is. Comparison requires that two pieces of evidence arrive to the lab, one as the control, one for comparison to it. For this there are about 10 different tests and include properties as simple as mass to refractive index. Comparison tests are always expressed in terms of probability or likelihood. In order for there to be "no chance" the probablilit would have to be .0000000000000000000000000000000000000000000000000000000 000000000000!!! Thats one out of the entire population of the world! |
Nylon fiber cross section magnified. |
Hair root Feather |
Traces in sole of shoe |
Can you describe these physical properties which are analyzed in trace evidence materials? Melting point Mass Density Refractive Index Color |
Can you describe these processes in trace evidence analysis? Electrophoresis Spectrophotometry Chromatography Mass Spectrometry Atomic Absorption Emission Spectra Neutron Activation X-ray diffraction |
Hair analysis: Did you know that: 7/10 people have brown hair, 1/7 have blond, 1/10 have black, and 1/16 have red? Hair is a very significant piece of evidence when considered by race. See below. Negroid: ....hair is flat in cross section. ....the pigment is dense ....the cuticle is thin ....the hair is very curly Caucasoid: ....cross section is oval ....pigment is even ....cuticle is medium in depth ....hair is rarely curly Mongoloid: .....cross section is round .....pigment is auburn .....cuticle is very thick ......hair is never curly There are three layers to hair which are forensically important: the cuticle.....overlapping external scales which helps in species identification. the cortex.....made up of spindle-shaped cells that contain the pigment, this can be used to i.d. an individual. the medulla....used in species differentiation and varies from person to person. Using neutron activation analysis, 14 different elements of a hair can be identified. Hair that is pulled out with the follicle still attached can be used for DNA identification. Blood type and some types of poisoning can be identified through the hair. |
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last updated
on: August 8,
2003
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