Chemical tests for GSR identification | Ballistics
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Clothing submitted to the laboratory will be examined to determine if a pattern of gunshot residues are present. There are basically three steps taken by the firearms examiner to process an item for the presence of gunshot residue.
The first step is to visually and microscopically examine the evidence. The presence of any gunshot residues found around the bullet hole as well as the shape and appearance of the hole will be documented.
The next two steps involve chemically processing the exhibit for gunshot residues.
The first chemical test conducted is called the Modified Griess Test. The Modified Griess Test is performed first on the exhibit because it will not interfere with later tests for lead residuesThe Modified Griess Test is performed by first treating a piece of desensitized photographic paper with a chemical mixture of sulfanilic acid in distilled water and alpha-naphthol in methanol. Desensitized photographic paper is obtained by exposing the paper to a hypo solution. The photographic paper will no longer be light-sensitive but will be reactive to the presence of nitrite residues.
The exhibit being processed is placed face down against a piece of treated photo paper, with the bullet hole centered on the paper.The back of the exhibit being examined is then steam ironed* with a dilute acetic acid solution in the iron instead of water.
The acetic acid vapors will penetrate the exhibit and a reaction takes place between any nitrite residues on the exhibit and the chemicals contained in the photographic paper. The resulting reaction will appear as orange specks on the piece photographic paper.
Other tests are listed in the video. Check it out.
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Clothing submitted to the laboratory will be examined to determine if a pattern of gunshot residues are present. There are basically three steps taken by the firearms examiner to process an item for the presence of gunshot residue.
The first step is to visually and microscopically examine the evidence. The presence of any gunshot residues found around the bullet hole as well as the shape and appearance of the hole will be documented.
The next two steps involve chemically processing the exhibit for gunshot residues.
The first chemical test conducted is called the Modified Griess Test. The Modified Griess Test is performed first on the exhibit because it will not interfere with later tests for lead residuesThe Modified Griess Test is performed by first treating a piece of desensitized photographic paper with a chemical mixture of sulfanilic acid in distilled water and alpha-naphthol in methanol. Desensitized photographic paper is obtained by exposing the paper to a hypo solution. The photographic paper will no longer be light-sensitive but will be reactive to the presence of nitrite residues.
The exhibit being processed is placed face down against a piece of treated photo paper, with the bullet hole centered on the paper.The back of the exhibit being examined is then steam ironed* with a dilute acetic acid solution in the iron instead of water.
The acetic acid vapors will penetrate the exhibit and a reaction takes place between any nitrite residues on the exhibit and the chemicals contained in the photographic paper. The resulting reaction will appear as orange specks on the piece photographic paper.
Other tests are listed in the video. Check it out.
For More Subscribe now...
#forensic #science #ugcnet
Join our whatsapp group:
https://chat.whatsapp.com/E8kMU67rlTK...
Here I am sharing videos about Forensic Science topics, Subscribe for more:
Channel Link: https://www.seevid.ir/fa/result?ytch=UCsQM...
4 سال پیش
در تاریخ 1399/04/05 منتشر شده
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