#forensicdivision

Cartridge Cases

📌 Cartridge cases are usually made of brass, a composition of 70% copper and 30% zinc.

📌Less commonly, they are made of steel or aluminum.

📌 Zinc andplastic materials have been used experimentally.

📌 Brass, plastic, and paper are used for shot-shell tubes.

📌 The main function of the cartridge case is to expand and seal the chamber against rearward escape of gases when the cartridge is fired. When a brass cartridge is fired in a weapon, the gas pressure produced by the burning of the propellant expands the case tightly against the walls of the chamber. If the brass is tempered to the correct hardness, it will spring back to approximately its original dimensions and make the case easy to extract. If the brass is too soft, it will not spring back and will make extraction difficult. If the brass is too hard, brittle, it will crack.

👉 There are three general shapes for cartridge cases: 🕵️‍♂️ Straight, 🕵️‍♂️ Bottleneck, 🕵️‍♂️ and, Tapered.

Almost all pistol cartridges are straight, whereas almost all rifle cartridges are bottle-necked. The bottle-neck design permits more powder to be packed in a shorter, fatter cartridge than would be possible in a straight cartridge, where the lumen is approximately the diameter of the bullet. Cartridges with tapered cases are virtually obsolete.

Handguns:

There are four basic types of handguns: 1. Single-shot pistols 2. Derringers 3. Revolvers 4. Auto-loading pistols (automatics)

1. Single-shot pistols- A single-shot pistol has one firing chamber integral with the barrel, which must be loaded manually each time the weapon is to be fired.

2. Derringers- They are a variant of single-shot pistols. Derringers are small pocket firearms having multiple barrels, each of which is loaded and fired separately. The traditional derringer has two barrels.

3. Revolvers- The revolver is the most common type of handgun in the United States. Revolvers have a revolving cylinder that contains several chambers, each of which holds one cartridge. The cylinder is rotated mechanically so as to align each chamber successively with the barrel and firing pin. The first revolver was produced by Samuel Colt in 1835–1836.

Q:- Why soil is considered as an Evidence? Ans:- Forensic soil scientists consider soil as any earth material that has been collected accidentally or on purpose and is related to the problem they are investigating. Though the technology isn’t perfect, soil forensics is considered as an important wing during investigations. Soil in includes rock, minerals, vegetation, glass, paint, asphalt, etc. The presence of these objects in that area helps to make that area of soil unique from other areas.

Q:- What quantity of soil sample is required ? Ans:- In most forensics cases, only about one cup of the top layer of soil needs to be collected.

Q:- How analysis should be performed? Ans:- Samples are dried before testing, to prevent further decomposition of the material in the soil. 👉 At the crime lab, the forensic soil scientist conducts chemical and physical analysis tests and compares the soil samples from the crime scene location with the soil sample found on the suspect or on his or her belongings. 👉 Another test for soil is ground-penetrating radar technology (GPR). Scientist use radar energy pulses to look for breaks in the soil’s structure. GPR helps detect anomalies in the soil, where radar energy is sent back to the receiving antennae. But the drawback- it is not always accurate, especially with heavy clay soils. In the end, with the use of soil forensics and GPR technology, scientists and investigators can make connections between differences in the soil and collected evidence. By identifying by the individual characteristics of soil, investigators can use this knowledge to help solve crimes.