Describe the process of four different methods used in forensic science and discuss its usage in locating evidence. Specifically describe how shoe casting and tire impressions are done, how ALS (Alternative Light Sources) is used to locate evidence, and discuss handwriting analysis and its various uses in forensic science.
Examples of Methods Used in Forensic Science
I. Process of Obtaining Casts of Shoe and Tire Impressions:
Facts from the California Department of Justice, Bureau of Forensics, Physical Evidence Bulletin, PEB 23 (Rev '98)
Process of Obtaining Casts of Shoe:
Note: Before mixing the casting material remove any loose debris like leaves and twigs, which may have fallen into the impression, but only if it does not destroy part of the impression.
1. Casting is a three-dimensional impression documentation for evidence.
2. The type of soil to cast from is the determining factor whether casting can be done.
3. Snow and fine humus soil are examples of excellent soil for casting. Casting is difficult in coarse soil.
4. The California DOJ recommends the following casting materials: dental stone, traxtone, or die cast
5. Dwayne S. Hildebrand, lead latent print examiner from the Scottsdale, Arizona, Police Crime Lab, recommends using dental stone. Hildebrand believes that dental stone "has proven to be much stronger, and therefore, does not require that reinforcement material be placed in the cast during the pouring. Most importantly, dental stone is more durable and harder than plaster of paris and can be cleaned in the laboratory with a potassium sulfate solution, with virtually no loss or erosion of detail from the surface."
(See Hildebrand, Dwayne S.(1999). Footwear, The Missed Evidence, A Field Guide to the Collection and Preservation of Forensic Footwear Impression Evidence, Wildomar: Staggs Publishing.)
6. This casting instruction is taken directly from the Physical Evidence Bulletin:
"The Dental Stone is mixed in the proportion of 1 lb./6 oz. of water and Die cast 1 lb./5 oz. of water. It is handy to preweigh one pound portions into large ziplock bags. Traxtone is prepackaged and takes 7 oz. of water to mix in its one gallon ziplock bag. Add the water ...
This solution is a 1,139 word description of four examples used in Forensic Science with sources cited:
1. Shoe Casting
2. Tire Impressions
3. Alternative Light Sources (ALS)
4. Handwriting Analysis