(Gun) Smoke and mirrors

[jimlongley]

Posted in Political Issues because I can envision DiFi and Chucky Schumer insisting that their states and the US develop a "Gunshot Residue Repository" so that crime guns can be immediately identified and traced, etc, etc, etc.

The latest issue of "Science News" (for May 5, 2012) includes an article about researchers developing a means for detecting the caliber of a gun from gunshot residue.

http://www.sciencenews.org/view/generic ... s_firearms_" onclick="window.open(this.href);return false;

My answer below was written and sent before I discovered that the online version of the article was a little more comprehensive, but not much.

RE: Smoking out clues

It’s not too much of a surprise that the researchers were able to distinguish between powder residues, they are, after all, chemically different as long as a different powder was used, but it’s a stretch to expect a particular residue to be the signature of a .38-caliber revolver and another to be the signature of a “9mm.” The problem is not enough data and too many variables, not enough guns and too many powders.

Strictly speaking, the “caliber” of a gun is merely its bore diameter, what seems to be being identified here is the designation of the cartridge, after all once again strictly speaking, both a “9mm” and a “.38-caliber” fire a projectile that is 9mm in diameter. There is even a revolver on the market which can fire both, or either, and several others without any modifications.

A: There are lots of different gunpowder formulations, and it is possible, even probable up to surety, that what one ammunition manufacturer uses for one cartridge combination, may be used by another for a different one, and that is not even considering the number of custom ammo makers and handloaders in the world. Gun powders are formulated to provide a specific impulse of energy through production of gas during a short duration burn, and a powder that works great in a 4 inch barrel just may not cut the mustard in a 3 inch barrel, both firing “9mm” and neither of the powders that work fine in those two might make a good powder for a 5 inch barrel, but one might work fine across .45 caliber, .40 caliber, 9mm and .38 caliber.

It is quite common to hear conversations, in the gun clubs of the world, about the advantages of using this powder as opposed to that powder, a rifle powder in a pistol cartridge, or a shotgun powder in a revolver in order, for example, to achieve better accuracy with less recoil, or faster cycling of a slide.

B: And then there is the question of which “9mm,” or which “.38-caliber,” we are talking about. In “9mm” alone there are no less than 16 different cartridges designated “9mm” (allowing for overlap) with the most common being the 9mm Parabellum, which I would speculate was the “9mm” in the article and some of those are also named “.38-caliber.” And .38-caliber (which in most cases is ALSO 9mm) also refers to another 9 plus cartridges, with the attendant cross pollination in naming.

And different bullet weights within specific calibers and/or cartridges sometimes require different powders in order to function well, even though they are all “9mm” or “.38-caliber” or “.45ACP” and so on.

In conclusion, in order for this process to be even close to valid, there would have to be a database of the signatures of each type of powder for every type of gun it could be used in, and which bullet weight, and barrel length, etc, a massive undertaking of questionable utility. In other words, unlike the CSI TV shows, there won’t be a magic scope that identifies the make and model of gun used just by examining the powder residue, it’s doubtful that even the caliber, much less the cartridge designation, would be strictly identifiable. While it may be possible to identify which powder residue was contributed by a particular gun, having both in hand, due to the factors mentioned above, and others, it is unlikely that just the residue will identify a particular caliber, even less so a particular gun.

Jim Longley

[OldCannon]

Maybe Chucky should first look in his own backyard, where the NY government recently scrapped their expensive and fruitless ballistics database.

Then again, he's never been a fan of that pesky "logic" stuff.

[gdanaher]

I can't see how this could work but presuming it did, and it could exclude certain samples from a crime scene, then perhaps it might be useful. I just don't see how Remington can make 9 mm kurtz on an assembly line this morning, switch to .45 acp in the afternoon, use the same powder material mix, and it show up after use and indicate the caliber fired.....

[Beiruty]

how about stab wounds and decapitation and dismembering ? Can they leave residue of evidence of the type and brand and serial number of the butcher knife used?

[gdanaher]

It might be possible to identify the manufacturer of a particular bullet based upon GSR. We all know that some of them smell differently or leave everything filthy at the end of a session. But looking at the bullet itself, it likely can be identified by manufacturer. But a 9 mm or .40?? Really?? On GSR?? Now everyone knows that the most poorly equipped crime lab can identify the owner of a knife used in a crime, and they can always do it it in about 47 minutes.

[Heartland Patriot]

SNIP

unlike the CSI TV shows,

Jim Longley

The sad thing is how many folks there are out there who think those shows portray things as they ARE, not as entertainment, or as they WISH they could be. I admit to watching the Vegas one, and the NYC one, for quite a while...I did my best to suspend my disbelief for the sake of being entertained. But, not too long ago, I sat down to watch an episode with my wife...and got ticked off and left in disgust. The whole episode was some sort of condemnation of the FN 5.7mm cartridge and the show making statements to the effect that it was super-rare and only for military use, stuff like that. Anyway, I said all of this, to sum it up thus: Do NOT be surprised if they come out with some CSI episode showing that they can track the rounds from some crime because of the powder...its all about imbedding ideas into the public conscious...after that episode on the 5.7mm round, I am CONVINCED.

[jimlongley]

SNIP

unlike the CSI TV shows,

Jim Longley

The sad thing is how many folks there are out there who think those shows portray things as they ARE, not as entertainment, or as they WISH they could be. I admit to watching the Vegas one, and the NYC one, for quite a while...I did my best to suspend my disbelief for the sake of being entertained. But, not too long ago, I sat down to watch an episode with my wife...and got ticked off and left in disgust. The whole episode was some sort of condemnation of the FN 5.7mm cartridge and the show making statements to the effect that it was super-rare and only for military use, stuff like that. Anyway, I said all of this, to sum it up thus: Do NOT be surprised if they come out with some CSI episode showing that they can track the rounds from some crime because of the powder...its all about imbedding ideas into the public conscious...after that episode on the 5.7mm round, I am CONVINCED.

Exactly my thoughts, and the reasons I have long since ceased to be entertained by the CSI genre.

[puma guy]

It has always been my understanding that nitro-cellulose powders are all pretty much the same. The "formulations" are actually just variations in coatings and/or granular shape to control speed of burn after ignition.

[OldCannon]

Exactly my thoughts, and the reasons I have long since ceased to be entertained by the CSI genre.

I think this perfectly captures the malevolent stupidity of CSI:

[youtube]http://youtube.com/watch?v=JMIHNiR3CP8[/youtube]

[Heartland Patriot]

Exactly my thoughts, and the reasons I have long since ceased to be entertained by the CSI genre.

I think this perfectly captures the malevolent stupidity of CSI:

[youtube]http://youtube.com/watch?v=JMIHNiR3CP8[/youtube]

I was quite the fan of Red Dwarf when I was stationed in England many years ago...best laugh I've had in a while, thanks.

[Kythas]

The sad thing is how many folks there are out there who think those shows portray things as they ARE, not as entertainment, or as they WISH they could be.

I remember reading one time several years ago where a man was acquitted of murder. One of the jurors in an interview mentioned that the forensics didn't provide the evidence like they do on the CSI show on TV and because of that, even though the other evidence pointed to his guilt, they voted not guilty.

Because of this perception, there are some courts now where they spend some time bringing in a forensic expert to testify that forensics is NOT performed like it is in the CSI shows, that those shows are for entertainment and do not accurately depict what is possible with forensics.

It's sad that our tax dollars and the court's time must now be wasted showing jurors that what they see on TV is just entertainment and does not depict real life.

Here's an article about what they're now calling "The CSI Effect": http://www.usatoday.com/news/nation/200 ... fect_x.htm

[Jim Beaux]

In the late 70's I was on a jury in which a female pusher shot and killed a policeman through the curtain of a window of her front door during a raid. It's hard to recall the facts but as I remember, the revolver had ammo from two different manufacturers & an empty chamber.

The police were able to discredit her testimony by showing the distance she claimed to be from the door when she fired differed from the evidence. (she fired multiple rounds)

The investigator testified that the powder in some of the rounds were spherical in shape & in the other flat (as in corn flakes). He further stated that the spherical being more aerodynamic would fly further than the flakes. The lab was able to "develop" the residue on the curtain by using a solution that reacted with the nitrite & then index the powder patterns with the empty shells & ammo remaining in the revolver.

Fascinating.

Regretfully, & thanks to the bleeding heart liberals who refused to do the right thing, the murderer has been free for at least 25 years.