Ballistics, a gun's "DNA"

T

thegluups

Prime Suspect
Every time a gunshot is fired, the gun leaves unique striations on the bullet. From there, you can match the bullet to the gun by testfireing it. I hope that until now, I'm correct... My first question is : I suppose, that, if these striations are unique, then matching a gun to the bullet in a case would be regarded as solid evidence? Would matching this same bullet with a gun be enough to get an arrest/search warrant, and how would it sound in a courtroom. I know it all depends on the context...but still...If any one could help, that would be great! :D
 
Well you would think that comparing the bullet that killed someone to the gun that belongs to someone else and finding a match, would seal that case tight. But there are many variables that can affect the case.

For starters, who is the gun registered to? Is there evidence proving that this person who owns the gun, actually fired the weapon? Matching the bullet to the gun is one thing, but ultimately proving who pulled the trigger is another. :)
 
I am not a professional in this area, but have read some things to explain other variables. For instance, in some cases, a bullet hits something that smashes it so much that the striations are unreadable.
 
I'll have to pipe in since this is my area of specialty.

To the OP:
Not all guns leave stria behind on the bullet (or casing) that are high enough quality for a positive association or a "match". I have personally test fired weapons, and looking at the test fires produced by myself, they was not suficient quality/quantity of correspondence between test fires produced sequentially for a "match". Secondly, unlike DNA and fingerprints, the marks a particular firearm will leave on fired bullets and casings will change overtime. This is due to continued wear & tear on the firearm, as well as possible damage/abuse to the firearm.

As far as if a match between an evidence bullet/casing and a test fired sample being enough evidence for an arrest that's a very difficult question to answer. My first question back to you is how is this match possible? Where did the test fire come from? Was it a firearm that was seized from a suspect during a search warrant? If so then yes possibly it would be enough evidence to arrest the person who was in possesion of the firearm. There is no sure-fire (pun intended) was of knowing who the owner of a firearm is. In the United States (except in select few states) firearms do not have to be registered. Sales receipts between a licensed dealer is required, but if that initial purchaser (non-gun dealer) then goes and sells the firearm, there is no requirement for any type of background check/tracking system.

If the firearm is a "found" gun, test fired, and a positive association is obtained using an automated database system (see NIBIN at the ATF website), then who do you arrest? You would have to prove that the original purchaser was still in possession of the firearm at the time of the crime- see above paragraph for further information.

There are only two states that have a system in place where all new firearms are test fired, and entered into that specific state's computer database system. Federal law prohibits all new firearms from being entered into the national system, and common sense, logistics, and the actual science behind firearms identification prove that such a system would be fruitless at today's technology level. The first reason has already been touched upon. That is that the individual characteristics of that firearm change over time - and most rapidly after the first few shots out of the factory as the weapon "breaks in". The second reason is that a database that would contain every new firearm sold would be so huge, and contain exhibits that vary so slightly that the current computer technology is not able to differentiate them.

In support of the second posts comments the bottom line is that unlike fingerprints and DNA, firearms identification links back to the tool used, and not to the person who pulled the trigger...it might be possible to get fingerprints or DNA off the firearm - but then we are back to someone who touched/came in contact with the firearm but not who pulled in the trigger in the crime.

If you have any other questions, feel free to post back.
 
Thanks for the information. :) You've answered a lot of questions, and cleared up a lot of misconceptions about the field of ballistics.
 
Also, there could possibly be other marks on the bullet created afterwards- like in "Creatures of the Night" on CSI: NY. It may not be common, but I think it could be hard to determine the gun marks from other marks.
 
Well then, I stand corrected once again. :p

But then again, I'm not the professional. It's always great to learn to things though. :)
 
Thanks a lot, I'll just reask one question, if you match a bullet to a firearm found at the scene, it's registered and you find the owner, would this be enough to get a warrant?
 
I couldn't answer that question. We just don't have registered firearms here. I guess in theory I would have to say yes, but I'd still expect investigators to visit the person who the firearm is registered to and ask him/her where the gun they have registered is. If they say the gun was sold/stolen, you would probably need more evidence to arrest them.
 
It would be enough to get a warrant to search the owners house and get prints and swabs too, then you would have to check the weapon for prints and get a match with the owner to get an arrest.
Hopefully it was checked for prints when it was found tho.
If there is a match it should be strong enough to make an arrest, an as ForensicsGuy said if they say it was stolen, this is what they would probably say, then if the warrant covers a search then they would look for evidence to put him at the scene, and depending on how the gun was held and the type of gun, the shooter could have a cut on his hand where the top slides out, um that may be confusing but i don't do guns, if anyone knows what i mean.
When the gun is shot the top slides back on some guns at quiet a speed and if the gun is being held with two hands, one on top of the other it can cut the persons hand.
Sorry for my rambling, hope this makes sense.
 
See I think you'd have already run prints and DNA on the firearm. If you happened to get a print match off of print records on file, you'd have grounds for "hauling them in for questioning".

If there was a DNA match, they would most likely already be a convicted felon for their DNA to be in the system, and as such you could get a warrant because felons are usually prohibited possessors, unless they have had their civil rights restored.

I don't see investigators being given a warrant by a judge based solely on sale records. Think about it like this so that you understand the firearms mentality in MOST of the United States. If someone had been killed by bashing their head with a hammer, and the hammer was found at the scene. The hammer had either a serial number, or someone scribed their name on the hammer, so you knew who at one time owned the hammer. Would you jump on that information and arrest them? Or would you check and see if there was any reported stolen hammers by that individual. Would you go visit the owner and interview them, and then based on the information obtained from talking to them, shift your investigation towards them.

There are so many scenario possibilities where the owner of the hammer did not strike the killing blow, arresting someone because they at one time owned the hammer wouldn't keep that person in jail for long at all. You would run the risk of alerting the person they are suspects in a criminal investigation, and have them flee once they are let go on a lack on evidence in that case. Finding prints and DNA on a hammer they admit was once their's is also useless information, one would expect someone's prints or DNA on a hammer they admit owning or having had owned in the past.

You have to remember that in the United States there isn't the same legal stigma to firearms as there are in other countries. A firearm is little more than a heavily regulated tool.
 
In some situations it can get you a warrant if it is the only thing you have to go on, but your right, i know it ain't going to shift the whole investigation to the owner, but as you say it's enough to bring them in for questioning.
 
Forensics_Guy said:
I guess in theory I would have to say yes, but I'd still expect investigators to visit the person who the firearm is registered to and ask him/her where the gun they have registered is. If they say the gun was sold/stolen, you would probably need more evidence to arrest them.
Click to expand...

And that's kind of what I said earlier on. A lot of people could have had access to the same gun, so finding a match isn't really enough in some cases. But it's different with every lab/country, and every investigation. :)

But I could be wrong once again.-Here in Canada you can't get a warrant on ANYTHING unless you can prove something, which doesn't always happen because funding for labs is really bad over here. :p
 
When I first saw the subject, I thought it was a fic, lol.

But I'm not a professional in this. So I'm not going to answer, hehe.
 
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