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Posted: 7/18/2008 3:32:02 PM EDT
now we all know people who claim that space-shuttle ninja CSI teams are so good they could trace spit back to god- (though a big glowing swimming pool in a crater on what was once an abortion clinic wouldn't be hard to piece together
 ), how good are ballistics teams really? how much can they REALLY find out? i mean i've read on here from a few of the smarter guys that ballistic fingerprinting is just BS-. Now I got in a debate with my brother yesterday- and we came to this question-Say they find that a murder weapon was a 1911. say they find two suspects with motive, shaky alibi's, both with 1911's, both with the same load (both the same make of 1911), could they tell one was the murder weapon and one was not? EDIT: could they trace fragmented 5.56? how much could be found out from doezens of pieces of lead and copper? and- what are the odds of getting a good recoverable bullet |
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Posted: 7/18/2008 3:34:57 PM EDT
[#1]
Yes
The barrel, firing pin and chamber leave unique marks on the bullet, primer and casing. |
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Posted: 7/18/2008 3:41:19 PM EDT
[#2]
So, all guns, leave different marks?, do manufactures make them that way, or is it due to the different wear on the guns.
For example, I have 2 Beretta 92's, both were bought new and both have about the same round count and usage, could a ballistics team find a differance between the two looking at bullets fired from each one or do all Beretta 92's have the same barrel rifling use the same firing pins? |
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Posted: 7/18/2008 3:43:57 PM EDT
[#3]
There's enough variation in the manufacturing process to provide a degree of individuality. |
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Posted: 7/18/2008 3:44:18 PM EDT
[#4]
It is as much art as science.
Same as fingerprints. given your scenario where it is either this gun or that gun, the answer is probably. but I have 'heard' that some firearms fresh from the factory can be damn hard to distinguish between each other. There is a write up disputing 'ballistic fingerprinting' running around. |
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Posted: 7/18/2008 4:14:43 PM EDT
[#5]
I don't know exactly how good ballistic evidence is, but I do remember that the main reasons that "ballistic fingerprinting" wouldn't work were that
1. The database would be too big. Ballistics is designed to compare a specific suspected murder weapon to a specific bullet. You can't really build a database of 10 million guns and compare bullets to every one of them - you'd get thousands of probable hits. 2. Ballistic marking patterns change as the gun is fired. You get the best results if the test firings are the next rounds fired after the rounds fired at the crime. The more rounds fired in between, the worse the comparison. Taking rounds fired from brand-new guns and hoping to compare them to crime scene bullets and cases from guns that may be years old and have hundreds or thousands of rounds through them probably isn't going to work very well. |
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Posted: 7/18/2008 4:46:50 PM EDT
[#6]
If the firearm is recovered, it's not that difficult to do a comparison with any projectile evidence found at the scene. The question is, who pulled the trigger? Just because a person is in possession of the gun doesn't always mean they were the shooter.
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Posted: 7/18/2008 4:49:05 PM EDT
[#7]
I've even seen situations where they've pulled bullet profiles from a sign that was shot. They used some sort of wax on the holes in the sign and used that to recreate the lands and groves of the bullet that made a hole and matched it to a weapon.
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Posted: 7/18/2008 4:49:47 PM EDT
[#8]
This. |
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Posted: 7/18/2008 4:56:30 PM EDT
[#9]
Very simple to defeat.
#1 have after-market barrel #2 have spare firing pin #3 have spare extractor After use, take torch or welder to all three and toss in river. ETA: replace with originals Result: Good Luck CSI 
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Posted: 7/18/2008 5:00:06 PM EDT
[#10]
Maybe to a type of weapon, but I don't think there's any way to match that to a particular weapon. |
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Posted: 7/18/2008 5:07:03 PM EDT
[#11]
Yep. Why do you think precision freaks can't just go out an get a load that worked extremely well on an identical rifle and expect it preform exactly the same? |
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Posted: 7/18/2008 5:08:53 PM EDT
[#12]
From what I saw they shot another stop sign with a rifle, took an impression of that hole and matched the two up well enough to convict somebody, so YMMV. |
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Posted: 7/18/2008 5:17:04 PM EDT
[#13]
what if they change loads? |
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Posted: 7/18/2008 5:18:31 PM EDT
[#14]
From what I saw the molds they used matched up the rifling marks that could be recreated from the holes in the metal signs....in such a situation a different load may not make a difference. |
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Posted: 7/18/2008 5:20:30 PM EDT
[#15]
Where did you see this? |
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Posted: 7/18/2008 5:23:29 PM EDT
[#16]
One of them true crime shows where they follow a real life case. I've never heard of such a thing before, but there's lots of things I've never heard of before.... |
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Posted: 7/18/2008 5:23:57 PM EDT
[#17]
On CSI
There is NO WAY the land and grooves would be left on the sign. The rotation would have to be just right, coupled with the speed, then equal to a perfect slice of land/grooves as it slides through the object. |
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Posted: 7/18/2008 5:27:31 PM EDT
[#18]
I doubt it would be worth the manhours and expense to CSI some bubba shooting signs unless they were just really bored and had a really big rash of signs being shot. That's even it it's possible, which i highly doubt unless Searchie has come out with a new stop sign vandalism kit that I don't know about.
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Posted: 7/18/2008 5:30:29 PM EDT
[#19]
No, one of those shows similar to what A&E does on real crimes. They follow a particular case and some of the evidence in the case for half an hour. |
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Posted: 7/18/2008 5:31:05 PM EDT
[#20]
I believe it was in connection with a murder case. |
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Posted: 7/18/2008 5:31:06 PM EDT
[#21]
Or unless that bullet was a pass-through from the dead guy lying on the side of the road. I still don't see them being able to get any better than maybe a general idea of the number of lands and grooves. Certainly nothing regarding striations inside the grooves or on the lands. |
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Posted: 7/18/2008 5:36:10 PM EDT
[#22]
Sounds alot like the now defunct 'lead batch' evidence. Where the FBI was claiming that they could match bullets by trace elements in the lead. Or the 'fingerprint expert' that ended up getting some cases tossed because he was making stuff up, claiming 3-5 point 'matches' were irrefutable etc. (think that was in New York) He got away with it until DNA came along. All it takes to get a conviction is a lawyer that isnt smart enough to impeach the 'expert witness', or people on the jury that arent smart enough to get out of jury duty. |
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Posted: 7/18/2008 5:37:27 PM EDT
[#23]
What about Glasers? Do lands and grooves show up?
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Posted: 7/18/2008 5:39:24 PM EDT
[#24]
Yep, I watched one of those where they said a K-9 tracked a guy for over 20 miles, even though the guy took rides in 2 different cars during the journey. Sometimes fact isn't as cool as fiction
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Posted: 7/18/2008 5:52:54 PM EDT
[#25]
Also I would assume they already had a suspect and firearm to match it to correct? Either way,thats fascinating stuff. |
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Posted: 7/18/2008 6:04:50 PM EDT
[#26]
That depends on how smart the guilty man is, and how much gunsmithing he's capable of doing.
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Posted: 7/19/2008 3:51:05 PM EDT
[#27]
Not even gunsmithing. Just shoot a lot of rounds down the barrel or Tubbs final finish. Pistol barrels take a long time to wear, though. But with the ease of getting new barrels, only a stupid criminal wouldn't through his barrel away after doing the deed. Good thing there are lots of them around. 
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Posted: 7/19/2008 4:12:10 PM EDT
[#28]
All ballistics can do is assign a probability to a question. The question is usually " was this bullet found at the scene ( or in the body) fired from this gun", or " was this shell casing found at the scene fired from this particular weapon".
A well schooled and experienced forensics tech can tell to a high level of probability that a particular bullet or shell casing was or was not fired from a specific gun. If they testify that they are 100% certain then they are full of shit. No science is 100%. Under ideal circumstances science gets in the 99+% range but it is never 100%. Forensic science is hugely a matter of opinion....opinion based on a number of factors. Good factors can be education, an understanding of the physical sciences and years of experience. Bad factors can be an overpowering personality, certification and licensure that is not supported by skills, many people fall for the old "he has a degree and is an expert so he must know what he's talking about crap". A lot of people have been convicted based on "expert testimony" that was nothing but pure unadulterated bullshit. For an example google the "snaggle tooth killer" case from Pheonix. A classic example of a murder conviction based on bullshit testimony that was ramrodded down the juries throat while other evidence was sidelined. |
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Posted: 7/19/2008 4:24:12 PM EDT
[#29]
WAY. I have several quarters that were shot at 100yds with my .223 and you can clearly see the impression left from the lands and grooves in the holes. I'd take a picture of it if I could, its quite obvious and I've made a point of showing the marks to non-shooters as I think its kinda neat. |
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Posted: 7/19/2008 4:54:17 PM EDT
[#30]
Marks from them and actual impressions good enough for comparison are two different things. People think any portion is comparable. That is not true. The amount, depth, length, and width are all critical into having a valid sample for comparison. |
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Posted: 7/19/2008 4:55:58 PM EDT
[#31]
Use bullets that shatter into a billion pieces.
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Posted: 7/19/2008 5:01:59 PM EDT
[#32]
Not fucking possible.  |
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Posted: 7/19/2008 5:03:38 PM EDT
[#33]
Maryland's ballistic "fingerprinting" system is about 70% accurate on average, with the accuracy being largely dependent on the human doing the final analysis and interpretation.
More info in this thread: www.ar15.com/forums/topic.html?b=8&f=29&t=316348 It would be correct to say that police ballistics techs are capable of determining with a reasonable degree of certainty whether or not bullet X was fired from Y gun. Obviously, trying to analyze a fragmented, incomplete or severely deformed bullet increases the degree of difficulty for the examiners. All of these technologies are just individual tools in a toolbox. They are best used in ways that complement one another rather than separately. No technology is 100% foolproof, and TV shows like CSI are basically bullshit.
Correct.
Concur. The best they'd be able to get would be the general outline of a portion of the bullet as it was when it struck the sign, which might tell them the general type/caliber of the bullet. But you're probably not going to be getting enough of an impression of the rifling grooves in order to match it to a particular weapon. |
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Posted: 7/19/2008 7:28:22 PM EDT
[#34]
wow, two very different opinons seem to be forming
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Posted: 7/19/2008 7:36:20 PM EDT
[#35]
If one were to change out barrel, extractor, and firing pin, then police up his brass after shooting, there's no fucking way they'd be able to match a bullet to a weapon.
And if one uses frangibles, they're even more fux0red. Simple fact. |
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Posted: 7/19/2008 7:44:09 PM EDT
[#36]
The problem with ballistics and other forensic sciences is that they are given too much weight in the public mind.....and frequently counted on too heavily by DA's. They fail to put in the time, effort and research to present a complete case for a jury that is multilayered and answeres many questions from many perspectives. DA's can fall into the trap of "it's sciences so it must be right". They hammer away at juries about the "evidence" failing to acknowledge that often the evidence is actually physical matter that is interpreted by a human and subject to whim, mistake, bias and error.
A prosecution that relys too heavily on forensics at the expense of other factors is one that has grave potential for injustice. You can have a case where the defendant has a good alibi from friends that shows that it was impossible for him to be present at the scene of the crime and also have an "expert witness" testify with a sackful of useless degrees that the "evidence irrefutably proves the defendant was at the scene of the crime". Who do you think the jury will believe? An expert who happens to be in error, incompetent, wrong or just plain biased. Or the defendants friends who might be telling the truth or might be lying for the friends benefit. Without supplemental evidencec and facts it would be all to easy for a jury to convict someone on the basis of an expert who was in fact an incompetent. Ballistics, fingerprints, odontolgy even DNA are not infallible. They can and have been misused and abused to do injustice. |
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Posted: 7/19/2008 7:45:59 PM EDT
[#37]
Now days, with the advent of CNC machining centers, it's going to be a lot harder to prove "uniqueness". The cutter path, rpm ect will be the same on every piece made. Same for button rifled barrels. Every barrel that button went through will have just about the same characteristics. |
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Posted: 7/19/2008 7:54:01 PM EDT
[#38]
I brought up this subject last week. I'm a machinist, and I know that if I'm running a long order of parts and I'm using the same tooling for each part, they they are all the same until a different cutting tool is used. Same deal with rifling a barrel. I don't know how they do it but wouldn't they use the same tool for as many barrels as they could, and wouldn't these same barrels, if fired leave the same kind of marks on the fired bullets? |
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Posted: 7/19/2008 8:23:54 PM EDT
[#39]
clap if you want tinkerbell to live!!!
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Posted: 7/19/2008 8:32:26 PM EDT
[#40]
I saw a website once that detailed the real way they do it, and the problems with what they do. I just can't find it anymore. If i find it ill let you know.
Edit: Found it. www.firearmsid.com/index.htm uh... I hope its accurate, when i read it 6 months ago it seemed to be. but yea, some new parts and you should be good to go. |
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Posted: 7/19/2008 8:48:00 PM EDT
[#41]
I have shot a lot of living animals with bullets and retrieved those bullets. I mean a lot like 200 or more.
In rifles.... Very few would have been in any shape to compare. Most of the lead is deformed into the shape like you had hot strains of hair and pressed it into the lead. Or broken into a lot of small pieces. The jackets are mostly in several pieces except the base. The base is almost always deformed and it would be almost impossible for anyone to claim two different deformed bases are from the same gun. At least from any evidence I have inspected. Pistol rounds are often in near pristine condition or completely deformed with no real reason for each differing results. Just my unscientific observation from 30 years of retrieving them and studying them for identifying marks, |
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