So can you tell if a Shotgun was the one used in a crime..

"Prooved" seems an entertainment stretch. Unless the victim was shot with a 12 gauge and the suspect was in possession of a 20 gauge....

There's no rifling like there would be with a bullet, but if the peelers had recovered fired shells, they might be able to show a very different firing pin strike on the recovered shells vs that made by the one owned by the suspect, for example.

Almost seems like it would be easier to positively rule a shot gun out vs prove it is the actual murder weapon.

I got an FN fal clone from Africa that had blood on it and bone chips in the action.
I'm pretty sure some people did something.
Either the murder weapon or weapon held by someone gettin murdered.

Also assumes that the owner didn't swap barrels which is a 30 second job with most pump shotguns

Murdered with a 12, Suspect's gun is a 20.

On the reverse end of things... where you have the shotgun that was used (and the individual that used it...) it's possible to verify or refute the shooter's claim of where they were at the time the shot(s) were fired if the victim's position is known... Distinguishing between true accounts and flat out lies (along with all the carefully crafted stories...) is everything in a homicide investigation...

Each shotgun fires a very predictable pattern if every factor remains the same (no ability or time to change the existing choke before investigators were on the scene along with the same ammo)... and you can determine from it pretty much exactly how far away your shooter was when the trigger was pulled if the ammo used is also known. That was the case the only time I ever fired a single shot on the street - all those years ago...

Just one more reason why anyone involved in a shooting is very smart to stick to a true account of their actions at the time....

A side note.. in my era (1973 to 1995) more than a few forensic breakthroughs began down here in paradise - one of them was the tech who thought to bring a set of wood dowels with him to determine exactly where the shooter was inside a room where rounds had been fired. You inserted the wood dowel in a hole in the wall and it pointed to exactly where the round came from. Another advance was the first time any crime scene type ever lifted a fingerprint off of the skin of a newly deceased victim (and that was in my city at the scene of a double homicide at an exercise place...).

Could the age of gunshot residue be determined, I wonder?

I know that someone could clean their gun and destroy the evidence, but could the GRS from a dirty gun be "dated"? Maybe if the gunk left in and around the action has solidified to their point that it can't be fresh. That is to say, a clean gun is more suspect than a dirty gun with old unburnt powders proving that the gun had not been fired recently?

Some pretty good answers and some far fetched. Odd Job did the best.
Here’s what can be done with a shot gun, when they have the suspected weapon and evidence from the crime scene.
They can determine approximately how far the suspect was from the victim. When shot from up close, the gunpowder that it still burning hits the skin and leaves what is called gunpowder tattooing.
If there are empty hulls at the scene, they can be matched to the gun.
The gun leaves marks on the hull. The extractor mark, the ejector mark, chamber marks and breach face marks.
The breach face marks are the most important and are left by different things. First are the tool markings left by the cutting tools. Then there are shear markings from the firing pin hole in the breach face. Most of the breach face marks will be located on the primer.
This is how those marks get there. When the gun is fired, pressure expands the metal portion of the hull. When the hull is extracted the chamber will leave marks on the metal sides of the hull’s rim. The extractor will also leave a mark. If the gun is a pump are auto, as the hull is extracted it will Hit the ejector, which will leave a mark.
When fired the hull is also pushed back onto the breach face. This will transfer any tool markings.
Here’s the most important part, when fired the primer is pushed back. Some of the primer gets pushed into the firing pin hole. This is called primer flow back. If there is any movement, up, down or sideways, the firing pin hole hole will shear The flow back leaving marks. The firing pin will also leave marks.
I, myself, do not deal with shotgun shells, just rifle and pistol cartridges. Here are some of the pics I take and look at.
This is the firing pin impressions from a Glock. Two different cartridge cases that were fired from the same gun.


This is a 3D pics



Here aer the shear marks matched up.



This is from a different gun.

Thanks Gunny - this is the kind of evidence that every investigator hopes to bring in front of a judge...

Remember; TV and movies are just that, TV and movies.

Gunny has the microscopic pics that will prove gun "A" fired shell casing "A", etc. While it is true that one may swap a barrel after a crime making the rifling impressions different on a recovered bullet vs a test-fired bullet with the different barrel, but it's pretty hard to swap a breech face or alter the micro-markings left on a primer from a firing pin swipe.

Stay safe.

DocRock said:

Unless the victim was shot with a 12 gauge and the suspect was in possession of a 20 gauge....

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Can it even be determined what gauge? Shot size yes, recover the volume of shot to determine an estimated original shot volume yes. Unless a shot cup, hull, or discarded rounds (or gun) is picked up it seems very unlikely you could definitively determine much unless it was a slug... and even then there are sabot slugs so....

WestKentucky said:

Can it even be determined what gauge? Shot size yes, recover the volume of shot to determine an estimated original shot volume yes. Unless a shot cup, hull, or discarded rounds (or gun) is picked up it seems very unlikely you could definitively determine much unless it was a slug... and even then there are sabot slugs so....

Click to expand...

Gun, hull, and wad conclusive. Payload over an ounce indicative.

Riomouse911 said:

Remember; TV and movies are just that, TV and movies.

Gunny has the microscopic pics that will prove gun "A" fired shell casing "A", etc. While it is true that one may swap a barrel after a crime making the rifling impressions different on a recovered bullet vs a test-fired bullet with the different barrel, but it's pretty hard to swap a breech face or alter the micro-markings left on a primer from a firing pin swipe.

Stay safe.

Click to expand...

It can be done on many shotguns in less than a minute. Some without any tools, or only a pin punch. However, the wear on that bolt/breech lock will be different than the wear on the receiver. While not prima facie level evidence, a good prosecuting attorney could possibly make something of the fact that had been recently changed.

I was asked to participate in an action designed to catch a bad guy with stolen fishing equipment years ago... I had a commercial fishing background (tackle shops, mate on charterboats) before getting into police work and posed as a high end tackle buyer looking for a "real bargain"... The ploy worked and we caught him with high end gear, a half dozen big game fishing reels and rods - that just happened to have the victim's name engraved on them in several places (reels that retailed for $500 to as much as a 1000 each... 45 years ago... ).

The thief also had been bragging about doing a bit of "contract work" and inside his apartment we found quite a few handguns - including three or four (both .22 and .45 autos) that didn't have barrels.... He was never proved to have been a contract killer - and died in prison from his other activities. I was told by skilled crime scene techs that we were probably dealing with a shooter given that it was common practice back then (mid seventies in the Miami area) for those kind of guys to use auto pistols - then discard the barrels after usage. Replacement barrels were easily obtained for both .22 and .45...

At the time I discounted what I'd heard - but years later came to believe that I'd been too close to someone that was in fact a very bad actor... To this day I consider myself to have been very lucky in those times since I was green as grass about street life and the folks who were living on the wild side of things... You live and learn I guess. Glad I'm long out of that world...

entropy said:

It can be done on many shotguns in less than a minute. Some without any tools, or only a pin punch. However, the wear on that bolt/breech lock will be different than the wear on the receiver. While not prima facie level evidence, a good prosecuting attorney could possibly make something of the fact that had been recently changed.

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Indeed, if attempting to sand, score or otherwise refinish a breechblock, human hands usually make sloppy alterations under microscopic examination as I am sure Gunny will attest. A true craftsman with proper tools may be able to duplicate Cnc machine tolerances, but Joe Crook with a pin punch or a file will not. It may not look exactly as it did when it was fired at the crime scene, but ham- handed work will be obvious to the examiner, the prosecutor and the jury with the proper presentation.
If you are referring to the swapping out of a breech block or bolt for another one, then yes, those may be changed quickly in many shotguns and also easily swapped in many rifles. But again, some gun-savvy people may have multiple shotgun breech blocks or rifle bolts in their possession and the ability to undertake the swap. Joe Crook? Probably not. As for handgun breech faces which are usually fixed in place, those would be much more difficult to alter without being obvious.

Stay safe.

Specific question in regards to Gunny's post. It seems to me that if you're comparing shell casings and matching them to the chamber when the time frame between the shots were fired is pretty close that it would be pretty easy to make a positive match. But what if the gun suspected to have been used is recovered years later after hundreds or even thousands of rounds have been fired through it. Would the normal wear from use change the markings enough to make a positive match harder, or even impossible?

jmr40 said:

Specific question in regards to Gunny's post. It seems to me that if you're comparing shell casings and matching them to the chamber when the time frame between the shots were fired is pretty close that it would be pretty easy to make a positive match. But what if the gun suspected to have been used is recovered years later after hundreds or even thousands of rounds have been fired through it. Would the normal wear from use change the markings enough to make a positive match harder, or even impossible?

Click to expand...

There would be some slight changes . I have matched cartridge cases that were fired ten years apart.

I've yet to see published proof of a shell casing from a shotgun being used as a positive match in a shooting. if there is such, it just means a double bbl is the one to go with. LOL

Anyone really familiar with a standard pump gun knows that it’s a simple matter to eject a fired shotgun shell into your hand if you choose... instead of allowing it to hit the ground. Fortunately those that do criminal stuff with weapons either aren’t very skilled or aren’t thinking about that sort of stuff when they’re breaking bad...

It is amazing how much Jollywood does not know about any type of firearm. That which is worse is how much “knowledge” of the public comes from Jollywood.

Must admit that if I was the one making a movie about bad stuff late at night (or in broad daylight) there are quite a few little things about guns that I would not want to see on film.... Young minds being what they are. On the street - a lot of what I saw or heard about were folks trying to imitate something they saw on the big screen. Just as soon that the stuff they're imitating isn't very useful at all.... But that's just me.