Are These Both Real Firearms?
Real Firearm Fake Firearm
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Can be very useful to determine where a bullet originated from, and the path it travelled. This can aid in understanding the placement of the shooter, as well as finding and recovering bullets.
Once a Bullet is Found - What Happens Next?
In each case what happens after a bullet is found (like the one in the image above) may vary, depending on the circumstances of the case, and resources available. But here is a brief summary of what may occur, and assume there is a suspect firearm recovered as well?
The bullet is examined in detail, for clear observations, weight, and potentially swabbed if there are any suspicious contaminates on the surface. (note: it is possible for human DNA to be present, if the bullet passed through a person before sticking a wall, a floor, etc).
After the bullet may be examined at a microscopic level, to investigate the unique markings potentially left on the bullet by the firearm.
These are marks left on the softer metal of the bullet by the harder metal of the barrel. Now not all firearms are rifled, but those that are leave these unique markings on the bullet. Rifling is done as it makes the bullet spin in a tight spiral as it leaves the barrel and subsequently has a straighter path than bullets fired from non-rifled barrels. The number of rifling marks, and the right or left hand twist can help determine the type of firearm to some extent. But exact identification can be made from from these marks specifically.
The Known Standard
Once the "crime scene" bullet is examined, if there is a suspect firearm that you wish to check if it is the one that fired the bullet, the next step is to create a "known standard" to compare the crime scene bullet too. There are a few different ways to do this, but one way is firing a bullet from the firearm into a test chamber.
Once the known standard is created, it can then be compared to the "crime scene" bullet. Specifically the rifling marks on each can be compared using a comparison microscope. In this way you can look closely at the unique rifling marks to determine if both bullets were fired by the same firearm.
Here is an example of such a comparison. The Crime Scene bullet is on the left, and known standard on the right, in this image. Look closely at the rifling marks left behind and ask yourself if you see similarities or differences!
What do you see?
Do you think both are similar enough to say they came from the same firearm barrel?
Coming Soon ...
More info about unique markings on cartridge cases that can also be used in a similar way to identify firearms...
There can be a wide variety to this evidence, but it usually falls into one of the following categories:
1. Firearms & Accessories
2. Ammunition - live or expended
3. Damage Caused by Firearms
4. Gun Shot Residue (GSR)
Firearms-Related Evidence Collection
A consideration during any forensic investigation, for any evidence, is how do you collect it?
It is always good to make detailed notes, and if possible, photograph evidence before touching it.
Firearms evidence often draws a lot of attention. But do your best to limit how many people interact with it. All firearms, accessories, and ammunition can be examined for fingerprints or DNA, while damage areas and GSR may be subject to chemical tests. As such, it is important to limit contamination.
Every person is a source of contamination or destruction of the potential forensic evidence. Do your best to:
•Handle as little as possible.
•Only touch to make SAFE and package.
•If you're not the one making it SAFE, or packaging, you shouldn’t be touching it!