Ballistic fingerprints over time

[wacki]

I know every firearm is different so feel free to pick a specific model if you desire.

How long does a gun fingerprint last? Lets say the FBI magically created a gun database within the next 24 hours that had a catalog of every firearm in the nation.

Now, how many times would I have to shoot my Savage 10FP .308 rifle before that database was out of date? What about a mini-14? Or any other rifled gun you know of.

Basically I'm wondering how quickly the barrels change.

EDIT:
Just so it's perfectly clear, I'm in an argument with an anti about gun control laws. This is in not about me in any way. So no need to give me advice about following the laws. :-D Just so this doesn't get tooo far sidetracked. This thread is about the practicality of instigating a ballistics database.

 

[CNYCacher]

Your question assumes that they actually CAN match bullets to guns that fired them.

It is my understanding that the techniques used to match a bullet to the gun that fired it are not reliable in the first place.

Based on my admittedly limited understanding of the subject, the practical answer to the question you asked is: "Zero Seconds"

 

[TX1911fan]

Seems like a scratch from a cleaning rod could do it as well.

 

[Sistema1927]

More "feel good" lunacy with no connection to reality.

It wouldn't take but a few seconds to change the "ballistic fingerprint" of any weapon.

 

[Lonestar]

Over the past 30 years or so, in manufacturing things has gotten very percise. With CNC and computers, gun parts will change very little over the years. Once a manufacture has a sucessful design nothing will change for years and that gun made today would be almost a carbon copy of one made ten years ago.

Its the stuff made before computers that will vary alot, because of more human hands and changes in machinery will slightly vary each product run.

I don't intend to commit murder, and I don't wear a tinfoil hat so the FBI fingerprinting bullets and casing to match them up with make and models of firearms never bother me much. From the research that I have done on the subject the database the FBI has is pretty vast. They can easily take a bullet and a casing from a crime scene and match it to the make and model of a weapon. If the evidence is in good condition they could probably zero in on the generation of that model, any modifications (barrel changes) and maybe even the manufactures run.

 

[wacki]

They can easily take a bullet and a casing from a crime scene and match it to the make and model of a weapon. If the evidence is in good condition they could probably zero in on the generation of that model, any modifications (barrel changes) and maybe even the manufactures run.

This is identifying the type of gun. This is not identifying the actual specific gun (say down to the serial number) which is what I'm trying to get at. Thanks for the response though. It was still informative.

 

[Lonestar]

This is identifying the type of gun. This is not identifying the actual specific gun (say down to the serial number) which is what I'm trying to get at. Thanks for the response though. It was still informative.

Nahh that would be impossible, The serial number does represent a manufacturing run though. If they are real good, I think they might pin down to what month the firearm was produced, but not exact serial number. Still if they can pin it down to a serial number FX41-??? and a suspect has a that weapon with a serial number FX41-123 that is pretty compelling. Of the million of weapon produced they are able to zero it down to a thousand. The LEO gets a warrant, test your weapon and if it matches, BINGO, if not they look at the other thousand owners for some sort of link to the murder victim.

Man I would love to be one of those CSI ballistics experts. I would get paid to pay with guns.

 

[wacki]

The LEO gets a warrant, test your weapon and if it matches, BINGO, if not they look at the other thousand owners for some sort of link to the murder victim.

This is the whole point of the database. Having this information beforehand. A "test bullet" must be on file before you can even buy the gun. If there are 2 million guns in the US there will be 2 million test bullets on file.

If they are real good, I think they might pin down to what month the firearm was produced, but not exact serial number.

Are you just guessing? Or do you have evidence supporting such a claim?

 

[Old Fuff]

There are several factors going on here. Depending on what evidence they have they may try to match:

A bullet to the barrel it was fired from. Not always easy. Metal fouling from subsequent shots may change the marking on the test bullet. Cleaning the bore before firing the test bullet can have the same effect. Remember, a close match doesn't count. It must be an EXACT match.

Match the impression left by tool marks on the firing pin and/or breechface to a primer and/or the cartridge head. This is the reason you often find a fired case inclosed with a new handgun. Here the trouble is that no one can say for sure that the case submitted by the gun dealer or gun owner to the authorities was really fired in that particular gun. Also any alteration to the breechface or firing pin tip will make any match worthless.

Two states currently have a "bullet fingerprinting" system in place - New York and Maryland. Neither have solved any crimes using it, although both have blown millions of taxpayer dollars trying.

If the tax-paying residents elect left-wing/Democrats they should expect to be stung with this sort of thing.

 

[SDC]

The answer will change depending on whether you're talking about the "automated" systems like IBIS (used in the NIBIN network), or whether you're talking about a one-on-one visual and manual comparison under a comparison microscope. Since the automated systems depend on a certain amount of statistical probability, they'll automatically discount some POSITIVE comparisons that should actually be left in the pool of "possibles". The manual/visual comparison method will catch those, but it takes so long (up to 5 hours or more, in some cases) that no-one has the time to actually sit down and do it without a certain likelihood of confirming or eliminating a likely match. For both, think of a series of overlapping regions along a line of subsequent shots; the automated systems will normally "pick up" shots fired within 100 rounds of each other (1 to 100, 200 to 300, etc., but not normally 1 to 1000), but double-blind tests of manual/visual comparisons will still confirm a match over the entire series.

 

[Pilgrim]

Theoretically speaking, if one is contemplating committing a crime where firearms evidence is left at the scene, i.e., bullets, cartridge cases, it is the sheerest lunacy to keep the weapon that can link that person to the crime.

Pilgrim

 

[Odd Job]

Here you go chaps:

http://www.firearmsid.com/Feature Articles/nichols060915/AS Response 110805.pdf

Start at page 13. That should put an end to all the speculation.

(you have not been charged for this research on your behalf )

 

[KC&97TA]

The Warm Fuzzy feeling of Ballistic Fingerprinting is thrown off track, when the owner is a heavy shooter and wears out barrels or replaces parts such as; barrel/fireing pin & polishing of the chamber, breachface of the pistol. To by pass such a sinister law, one just has to open up there Midway or Brownells catolog.

Most firearms owners won't wear out a weapon in several generations, a few people around here wear out 1911 & Rem 700 barrels about once a year.

 

[Firehand]

Go to http://smallestminority.blogspot.com, check the left sidebar for 'Why ballistic fingerprinting doesn't work' and click on it. Very big post with links to lots of information on this mess.

As to shooting, depends also on brand/type of ammo. They found that just changing brands of ammo could give a different result on the comparison of fired cases/bullets. On actually changing the marks, something with a hard jacket could change the physical marks left with a round or two in some cases.

 

[jfh]

If a million monkeys sat at a million typewriters/computers...

Heh. I too want to believe that ongoing changes in the firearm will negate the accuracy of such testing--but I wonder.

What these kind of tests come down to is a bit of probability-hypothesizing. Consider the (popular) history of fingerprinting, and the more recent history of DNA analysis.

With fingerprinting in mind--If I have it right, today's fingerprint databases look for hits based on a variable number of similarities, then home in further for more similarities. Once they do a search for (say) six points of similarity, they can re-sort for more--say twelve--points of similarity, and with that level of similarity, they now have a 99.9% (or whatever) that these prints match up.

The previous posts speak to the issue of getting down to a few points of simility--as noted, that's easy to do; we know that a sort by diameter, probable original weight, construction, etc., etc., will lead us to the genus (handgun/long gun) and type of firearm. BUT--if the database is woefully incomplete, then the liklihood of finding the actual firearm is fairly minimal.

And, this is without really considering getting test bullets from all firearms in the US, etc., etc.

In sum, it's currently impractical, at least in any sort of typical cost-benefit analysis. All we need to do to know that is to look at the Canadian Crime Gun database history, and a more recent history reported by the NJ (?) State database.

HOWEVER--given a few hundred antigun monkeys fiddling with it for the next hundred years, can such ballistic fingerprints turn into a completely credible forensic tool? I wouldn't bet against it--particularly if the population of firearms users continues to diminish.

 

[SDC]

In sum, it's currently impractical, at least in any sort of typical cost-benefit analysis. All we need to do to know that is to look at the Canadian Crime Gun database history, and a more recent history reported by the NJ (?) State database.

Canada doesn't have the sort of "ballistic fingerprinting" database that NY and Maryland do; samples up here are only entered from crime scenes and from "questioned" firearms that are seized or found. On that basis, it's been as successful as the US NIBIN system in matching crime guns to multiple incidents. Having said that, I think the "ballistic fingerprinting" end of things is a waste of time and money, if for no other reason than that it "floods" the database, and it ends up giving you a "possibles" list of several hundred, instead of 5 or 10; with a "possibles" list that big, you're back at the same point of having to work through them one at a time (4 hours each), saying "No, that one's not a match....no, that one's not a match....no, that one's not a match, etc." For all the time and money put into the NY and MD programs, MD HAS had a match, but the circumstances of the case made it pointless. In that case, someone with a legally-purchased pistol committed a shooting in a bar (with multiple eyewitnesses), and after the guy had already been positively IDed, they ran the test, and it came back to match the gun that was used. There's some more discussion on this topic in http://www.thehighroad.org/showthread.php?t=231557

 

[Old Fuff]

I don't think it will be an effective tool - ever. Why? because if the bore, breechface or firing pin tip of a firearm are altered in even the slightest way they can't get a match that will line up with the data base. Your fingerprints will always be the same. Once metal is altered the original marks cannot be reduplicated.

 

[SDC]

These characteristics change over time, but they change in consistent ways, and ONLY IN ONE DIRECTION (ie. a mark won't appear, then disappear, then re-appear again). Here are two shots of what the most successful half of the system looks at, the breech-face:

In this case, a drug dealer was picked up with a handgun that was matched back to an attempted murder (of ANOTHER drug dealer) several months before in the same area.

 

[jfh]

thanks for the thumbnails and link, SDC

You've addressed some of the issues involved.

The question is, do the politicians understand these?

 

[SDC]

The question is, do the politicians understand these?

In all likelihood, no; I think they probably have the same "quick-fix" mentality that they always do, ie. pass a law that APPEARS to do something, take credit when it appears that it MIGHT do something, then allow themselves to be carried off in the arms of their loving supporters. I'm sure that's how this nonsense was sold to NY & MD, and once something like that's in the law, how many of these laws are "un-made"?

 

[TX1911fan]

What irks me is that they get these laws passed in the name of "preventing" crime, but fingerprinting, etc. are useless for preventing crime. They are only helpful for solving crime. If solving crimes needs help, fine. Just tell us that's what it's for. However, if they say fingerprinting is for solving crime, they know we will counter with "well, if you are not preveting crime, then I need to be armed to protect myself." So they BS about how this will keep guns out of the hands of criminals, blah, blah, blah.

 

[Langenator]

Just wondering, but how much would lapping the barrel change the markings you'd see on a bullet?

And how much does bullet selection influence the markings? IE, cast bullets vs solid copper vs copper jacket vs bi-metal jacket, and the hardness of various allows used in the jackets?

 

[SDC]

It changes, but only within certain parameters; that's why, when an examiner does a comparison for legal determination, they'll only compare like ammo to like ammo (FMJ to FMJ, RNL to RNL, etc.). Lapping can change the very MINOR accidental markings on a bullet, but the major markings will still be identifiable.

 

[Car Knocker]

Lapping can change the very MINOR accidental markings on a bullet, but the major markings will still be identifiable.

I'm not so sure about that. A person can fire-lap a barrel with an aggressive abrasive until the rifling is darn-near non-existant. Both lands and grooves are re-contoured and the original contact surfaces are removed. THAT would certainly result in major changes to the markings on recovered bullets, yes?

 

[vynx]

I remember reading about how these matchs don't have to be 100%

As I remember it an FBI crime lab person would ID suspects based on fingerprint matches where they had something like 25 matching characteristics or points. This was because full complete fingerprints are hard to get and they usually had partial, smudged prints - think of how little print would be left on the side of a casing. In that situation they would say that the partial print matched 25 points to the suspects so he/she is the guilty person. Thats it case closed!

Some so called experts would give a positive ID based on as little as 6 matching points! I saw a show where these "experts" had their testimony ruled as not scientific (some TV newsmagazine like 60 minutes, 24 hours, etc.)
And the show went on to say they were only giving the answers the LEO asked for. (a lab "expert in Texas I believe).

Anyway, think of it this way if the original new barrel matched the recoverred bullit the same barrel that has been shot and cleaned 100 times will not match 100% but it might match say...70% for the so called expert that is good enough and he/she will testify Definetly came from your gun. Now if you scratch the hell out of the barrel then the match might go down to say 20% where they might still testify it was your gun but your attorney has a better chance of getting the jury to not believe their "expert".

I would not count on it at all. So don't plan on committing crimes with your gun and you should be ok.