Watching a cop show made me realize that matching projectiles to weapons with rifled barrels is plain enough but how do police ID smoothbore shotguns used in crimes?
If the shooter doesn’t leave spent shells around and doesn’t use rare powder/projectiles, how would the police go about making a match?
How reliable are matches based on firing pins or loading/extraction?
Need answer soon-ish, I’m heading to Reno next week.
You don’t. There is no rifling to match, and if you don’t eject a shell, there is no firing pin imprint to match either. Hell, if the victim only catches part of the pattern, it will be difficult to guess the gauge of the shotgun.
You might be able to guess the barrel length by measuring dispersal and distance from victim to shooter, but it would still be a very rough guess.
OP - the real question is how reliable is any forensic bullet matching? The answer is disappointing.
I suppose it’s possible if a slug is used and there is a significant and unique defect in the barrel.
Most of today’s slugs are saboted, so the only thing touching the barrel is plastic. Maybe it takes an impression better than lead would? Best in my mind would be a handloaded brass shell with no wad cup and steel shot. I’m pretty sure the steel shot would not pick up any impressions from the barrel.
You’ve piqued my curiosity, what do you plan on doing in Reno next week that you don’t want your shotguns traced?
One suspects that he intends to shoot a man, just to watch him die, and he wants to make sure that California’s criminal justice system doesn’t tie him to the crime.
The CA criminal justice folks probably won’t care to much…cause it would be a Nevada case.
if a resident of California shoots a man in Nevada, where are the survivors buried?
The wad separating the shot and powder will invariably be at the scene, and should pretty easily identify the gauge. Its possible if it is a plastic wad (most are these days) and the barrel isn’t perfectly smooth, it might have some identifiable marks from scratches in the barrel/choke. A step below that, the wad and shot may be identifiable to a certain lot number, especially if the manufacturer goes to the effort of marking wads.
You don’t bury survivors, you tie bricks to their legs and sink them in Lake Tahoe.
“Enhance, enhance.” - most TV CSI type shows.:rolleyes::rolleyes:
There certainly ARE ways that forensic science can provide evidence for shotgun blasts. Specifically, they can test two different shotgun pellets to see if they came from the same batch at the same factory. Tiny differences in the exact composition of the metal itself are detectable.
Suppose a woman is found dead with several shotgun pellets lodged in her torso, and upon searching her house they find a shotgun in the husband’s closet, along with a half-empty box of ammunition.
#1 They can test the pellets pulled from the woman’s torso to see if they are a metallurgical match to the shells still in the box.
#2 They can test the husband’s hands for gunshot residue to see if he has fired a firearm recently.
#3 They can test the wife’s clothing for gunshot residue to determine if the shot was fired from less than six feet away.
#4 They can test the husband’s shotgun to see if it has been fired recently.
There might be more tests I haven’t heard of.
Granted, it’s not as good as matching lands and grooves on a bullet, but it’s something. Sure, the husband’s lawyer might say “My client admits that he shot at a rabbit and missed earlier that morning, and whoever shot his wife could have bought his ammunition from the same store.” But if the prosecution can show motive and opportunity, forensics can certainly have the means nailed down.
Just stay away from Cal-Neva, OK? We don’t need any more bizarre hypotheticals.
There’s a current discussion on Quora that just came up: https://www.quora.com/Are-shotgun-rounds-traceable
Aren’t most slugs rifled these days, for firing out of smoothbore? I don’t think most people outside of Illinois, Indiana, etc. are using rifled barrels with sabot slugs.
Buying me a beer? But really, woosh: https://www.youtube.com/watch?v=8J7VQaWt1uQ
Crime scene techs may shoot their wad trying to id a shotgun. 
I was under the impression ballistic tests from shotguns aren’t conclusive evidence.
They can say at trial that a 12 gauge shotgun was used to kill the victim. A recently cleaned 12 gauge was found in the suspect’s house. But they can’t claim a ballistic match.
If movies are any guide, the real injury occurs when the victim backflips twenty feet.
Cite?
I have both barrels for my guns. Depends where I am using them and the amount of range I want as to which I use. Sometimes I don’t want the load to carry as far like when I am in more residential type areas or areas with heavy cover where I might not be able to see someone within range. Usually the smoothbore barrels for the rifled slugs are on so I can also protect the San domicile from vermin in the yard without stopping to switch barrels.
I’m not sure what you want a cite for, some specific bit seem questionable, or just upholding standards? I don’t think you can really cite studies that a shotgun wad doesn’t evaporate, or that a scratched bore will scratch a plastic plug sliding down it at 1000 fps.
The wad/shot lot number ID is more problematic, I’m not sure any manufacturer does even mark lot numbers on wads. I’ve only has minimal experience with shotshell reloading, and have seen wads with numbers and symbols on them, but never checked their meaning. Even lacking that though, with forensics these days, just batch to batch differences in pellet alloy and plastic composition might be enough to provide at least a general match. That’s why I said “may be” though.
This is really all from personal experience as a machinist/engineer/gunsmith, and past law enforcement experience. The LEO was decades ago though, I’m certainly behind the times with comparison tech. Of course, if you’re going for academic rigor, I would have to admit that most law enforcement evidence processing and analysis is not up to science standards, and often doesn’t have full foundational research support.