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Old March 9, 2014, 10:20 AM   #1
ATN082268
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Ballistics for Shotguns?

O. K. I'm sure everyone has seen the stuff on TV about how the police match up a bullet to a gun but can it be done to a shotgun or gun with no rifling?
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Old March 9, 2014, 11:22 AM   #2
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There are other ways of tying any gun to a crime.

The spent cartridge casing carries marks from the extractor, ejector, firing pin, and bolt face.

In the case of a shotgun the spent wad can be used to ID brand of cartridges.

If a slug load is used then they have a "bullet".

In some case's the shot used, lead/plated/steel.

The powder residue can give a indication of the shell manufacture.

There are more than one way to tie a gun to a crime and the police have them figured them all out. Good for the victim not so good for the bad guy.
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Old March 9, 2014, 11:57 AM   #3
Virginian-in-LA
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In the case of a shotgun, I doubt there is any good for the "victim".
BTW, ballistics is the science of the way a projectile behaves flying through the air. Analysis of the results on an event is forensics.
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Old March 10, 2014, 09:36 AM   #4
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Presumably investigators could also recover traces of lead from the barrel of the shotgun and run a metallurgic comparison to lead found in a victim or at a crime scene. I certainly wouldn't assume that just because a firearm isn't rifled that it could not be traced to a crime.
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Old March 10, 2014, 10:45 AM   #5
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Quote:
... I'm sure everyone has seen the stuff on TV about how the police match up a bullet to a gun but can it be done to a shotgun or gun with no rifling?
It should be noted that about 90% of everything you see on TV in this regard is nonsense or a gross oversimplification. CSI, NCIS and Law & Order show stuff all the time which borders on absolutely fantasy.
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Old March 11, 2014, 12:20 PM   #6
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There are matches, and there are matches...

I recommend watching the movie "My Cousin Vinnie". And pay attention to how the "experts" match the car and its tires.

In a court, what reality actually is, matters a little less than what the jury believes reality to be.

The ability of forensics to precisely match a fired bullet (or case) to a specific gun depends on the gun having something unique that can be identified.

General matches are much easier. The rifling marks are easily identifiable in that regard. For example, a .38 caliber bullet shows rifling with a 1 in 14" twist. This is the twist used in a Colt. The suspect/defendant owns a .38 revolver, but its a S&W. S&W uses a 1 in 18.75" twist. The bullet in evidence could not have been fired by the defendant's gun. That's a general ID.

If you have the right type of gun to have fired the evidence bullet, THEN it becomes a matter of whether or not the exact gun did fire it. And that needs some kind of unique mark that only that gun puts on the bullet. Not nearly as easy to do as it sounds like on TV.

Now, with a shotgun, its a bit of a different story. And only partly because of the lack of rifling. Everyone who doesn't already know shotguns don't leave rifling, and so cannot be "matched" will be told that, by the time they sit in a jury box.

So, the prosecution doesn't even try. And they don't need to. What they need to prove is that you had motive (a believable reason), opportunity (no vaild alibi) the murder weapon (here's where it gets you). All they have to do is prove you had a shotgun. Because of what everyone "knows" they don't have to prove it was your shotgun, they way they would have to prove it was your S&W pistol) only that you HAVE a shotgun, which is enough for nearly any jury to accept.

In many ways, using a shotgun to commit a crime actually makes it easier for them to get a conviction, despite the fact that many think it makes it harder, because "there's no ballistics" to match. (and yes, as was pointed out, "ballistics" is the wrong word to use, but its done all the time on TV)

ALSO, its not an absolute requirement that the cops physically have the murder weapon (or even the body!). Sure, makes it tougher to prove the case, beyond reasonable doubt, but not impossible. In the end, what it boils down to is whether or not the jury gets convinced (despite what reality actually is) to convict.

Another fictional account is in SHAWSHANK REDEMPTION. The main character in it gets convicted of killing his wife, despite the fact that the cops never recovered his gun. While the movies I mentioned are fiction, they illustrate the kinds of things to sometimes do happen in real life, to real people.
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Old March 12, 2014, 11:25 AM   #7
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Presumably investigators could also recover traces of lead from the barrel of the shotgun and run a metallurgic comparison to lead found in a victim or at a crime scene.
Sure they could. And they could prove what? That it was lead. Just like taking samples from your tires and comparing the rubber to rubber from tracks at the scene. Unless there is something specifically unique, they got nothing. Tread pattern, on the other hand might be unique enough for a positive match.

However, they can use that nothing to convince a jury, who knows even less.

(also, with modern ammo, the lead in shotgun shells never touches the barrel)
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Old March 14, 2014, 10:05 PM   #8
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Quote:
Quote:
Presumably investigators could also recover traces of lead from the barrel of the shotgun and run a metallurgic comparison to lead found in a victim or at a crime scene.
Sure they could. And they could prove what? That it was lead. Just like taking samples from your tires and comparing the rubber to rubber from tracks at the scene. Unless there is something specifically unique, they got nothing. Tread pattern, on the other hand might be unique enough for a positive match.
Different batches of lead contain slightly different elemental make-ups. The FBI used to do comparisons between bullets found in a body with those from certain manufacturers or even individual boxes of ammunition. I would assume they could or did do the same with shotgun pellets. It was discovered that while the basic science was okay, the FBI way overstated the statistical correlation between a particular bullet with a specific batch made by a particular manufacturer.

When this came out, the FBI quit doing the testing. Comparative lead analysis might be an investigative tool but probably cannot be admitted in court. Here is an article titled "The Current State of Bullet-Lead Evidence" which seems to sum it up pretty well.
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Old March 14, 2014, 10:47 PM   #9
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Comparative lead analysis might be an investigative tool but probably cannot be admitted in court.
I'm sure a properly done comparative test would be admissible in court. HOWEVER, how much good it would do, and for who's side is the issue.

Again, let me point to the scene in My Cousin Vinnie where the FBI expert testifies how they took sample from the tire tracks, and samples from the defendant's tires, and the results were "identical" . The prosecutor emphasizes the word, "EYE-DENTICAL" for the jury.

Then the defense points out that the specific tires on the defendant's car are the most popular (and most common) size and make of tire sold in the US. And how the test would give an "eye-dentical" result with any Michlin XGV radial.....

SO, essentially, while a isotopic analysis of the lead in the shotgun pellets used in the crime might be able to say, for instance, the shell used was a Federal, because Federal ammo is loaded with this batch of lead, its application to a specific case is problematical, as the defense need only bring up how many shells loaded with that particular isotopic mixture Federal made, placing the burden back on the prosecution to prove that is was shells from the defendant's box of Federal ammo that were used in the crime, and not someone else's Federal ammo....

Again, the counter balance to this is the fact that the prosecution need not prove it, if they don't bring it up before the jury.
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Old March 16, 2014, 02:03 PM   #10
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I'm sure a properly done comparative test would be admissible in court. HOWEVER, how much good it would do, and for who's side is the issue.
The standard for allowing scientific or expert testimony in federal courts and in some state courts is based on Daubert v. Merrell Dow. A Wikipedia article is here -- http://en.wikipedia.org/wiki/Daubert_standard. Primary factors for admitting such evidence are reliability and relevance. In considering relevance, a judge has to consider its probative value versus other factors like undue prejudice and the possibility of confusing or misleading the jury. There is a possible danger of a jury being misled about how important comparative evidence is. Some court may not allow such evidence. Others may. Judges have some discretion in this.

One of the leading cases on the use/misuse of comparative lead analysis came from my state if you want to do some reading on it. Ragland v. Commonwealth at http://162.114.92.72/Opinions/2003-S...ne+%2B+ragland
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