Reference no: EM132272754

Discussion :

There are a few tests used to determine if a person has fired a firearm recently. Older tests such as the Walker test involved the use of a piece of paper to collect the GSR (Heard, 2008). Newer tests involve the use of scanning electron microscopes, or chemical spectroscopy analysis, to determine the presence of GSR in a sample chemically and visually (Heard, 2008). An additional test for firearm handling and GSR is the Ferrozine test (Heard, 2008).

Ferrozine is a solution that shows the presence of iron and other heavy metals on the hand of a person who has handled such substances (Heard, 2008). The only test that could be considered conclusive would be spectroscopy analysis, due to results showing the exact chemical make up of the particles, showing 100% if the particle has atoms matching those of GSR (Heard, 2008). Ferrozine has its issues due to the fact that all heavy metals and iron will show up, therefor giving the possibility of having false positives (Heard, 2008).

The way that a evidence tech would collect a shoe print in dry dirt would be to make a cast of the impression. As with all forensic evidence pictures will first be taken, with and without measure, then the cast will be made and pictures again will be taken with and without measure (Lemay, 2010). The cast will be poured carefully and fully into the impression, then left to dry, covered and protected (Lemay, 2010). After that the cast is removed, packaged, marked and processed as evidence.

Tool mark impressions on the windowsill are able to be collected in a number of different ways. One way would be to remove the entire windowsill and package it as evidence (Gambino et al., 2011). Another way would be to make a putty cast impression of the tool mark on the sill. As always pictures would be taken before anything is done to the evidence, then after the putty has been applied. The putty is cast, and left to dry protected, then removed and packaged as evidence (Gambino et al., 2011).

Tire impressions in soft earth need to be handled carefully, however a cast of them will be made, albeit the cast might be slightly larger than the actual tire (Anon, 2006). As always pictures are taken. Then the cast is mixed and poured into the tire impression, where the best impression is of tread detail (Anon, 2006). The cast is protected as it is allowed to dry, then is carefully removed, packaged as evidence, and sent away (Anon, 2006).

A shoe print on a loose piece of tile would be the best thing to have. Since the tile is loose, the entire tile will be packaged as evidence, with precaution taken to preserve the print. Photographs will also be taken as per usual.

A shoe print that is made of dust will be lifted like a fingerprint, as the same theory applies (Lemay, 2010). A piece of tape or static plastic is used to lift the shoe print and attach it to a correctly colored backing (Lemay, 2010). As always pictures are taken before and after of the evidence.

References:

Anonymous. (2006). Guide for Casting Footwear and Tire Impression Evidence. Journal of Forensic Identification, 56(4), 635-641.

Gambino, C., Mclaughlin, P., Kuo, L., Kammerman, F., Shenkin, P., Diaczuk, P., ... Brown, C. (2011). Forensic surface metrology: tool mark evidence. Scanning, 33(5), 272-278.

Heard, B. (2008). Handbook of firearms and ballistics examining and interpreting forensic evidence (2nd ed.). Oxford?;: Wiley-Blackwell.

Lemay, J. (2010). If the Shoe Fits: An Illustration of the Relevance of Footwear Impression Evidence and Comparisons. Journal of Forensic Identification, 60(3), 352-356.