Firearms Microstamping Feasible but Variable, Study Finds

May 13, 2008

New technology to link cartridge cases to guns by engraving microscopic codes on the firing pin is feasible, but did not work equally well for all guns and ammunition tested in a pilot study by researchers from the forensic science program at the University of California, Davis. More testing in a wider range of firearms is needed, the researchers said.

Microstamping technology uses a laser to cut a pattern or code into the head of a firing pin or another internal surface. The method is similar to that used to engrave codes on computer chips. When the trigger is pulled, the firing pin hits the cartridge case or primer and stamps the code onto it. In principle, the spent cartridge can then be matched to a specific gun.

In October 2007, Gov. Arnold Schwarzenegger signed into law AB 1471, requiring that all new models of semiautomatic pistols sold in California on or after Jan. 1, 2010, be engraved in two or more places with an identifying code that is transferred to the cartridge case on firing. Similar legislation has been proposed in other states and at the federal level.

In March 2008, a report from the National Research Council, part of the National Academies of Science, described microstamping as a "promising" approach and called for more in-depth studies on the durability of microstamped marks under different firing conditions.

"Our study confirms the NRC position that more research should be conducted on this technology," said Fred Tulleners, director of the forensic science graduate program at UC Davis. Tulleners is former director of the California Department of Justice crime labs in Sacramento and Santa Rosa.

If successfully implemented, microstamping would be one additional piece of evidence for investigators to link various shooting events, Tulleners said.

UC Davis graduate student Michael Beddow looked at the performance of microstamped marks in one location, the firing pin. He tested firing pins from six different brands of semi-automatic handguns, two semi-automatic rifles and a shotgun. The firing pins were engraved with three different types of code: a letter/number code on the face of the firing pin; a pattern of dots or gears around the pin; and a radial bar code down the side of the pin. The engraved firing pins were purchased from ID Dynamics of Londonderry, N.H.

To test the effects of repeated firing, Beddow fitted engraved firing pins into six Smith and Wesson .40-caliber handguns that were issued to California Highway Patrol cadets for use in weapons training. After firing about 2,500 rounds, the letter/number codes on the face of the firing pins were still legible with some signs of wear. But the bar codes and dot codes around the edge of the pins were badly worn.

"They were hammered flat," Beddow said.

Tests on other guns, including .22-, .380- and .40-caliber handguns, two semi-automatic rifles and a pump-action shotgun, showed a wide range of results depending on the weapon, the ammunition used and the type of code examined, Beddow found. Generally, the letter/number codes on the face of the firing pin and the gear codes transferred well to cartridge cases, but the bar codes on the sides of the firing pin performed more poorly. Microstamping worked particularly poorly for the one rimfire handgun tested.

The researchers did not have access to patented information allowing them to read the bar- or gear-codes, and so could not determine if these remained legible enough to be useful.

Codes engraved on the face of the firing pin could easily be removed with household tools, Beddow found.

The researchers estimated that setting up a facility to engrave alphanumeric codes on firing pins would cost about $7 to $8 per firing pin in the first year, assuming that such marks would be required on all handguns sold in California, and based on the efficiencies associated with high-volume production costs, Tulleners said.

Tulleners said that a larger test of about 3,000 firing pins, from a wider range of guns, would allow for a more "real-world" test of the technology, as called for by the National Research Council report. About 2,000 makes and models of handguns are sold in California, compared with the nine tested, Beddow estimated in the study. A larger study would also help show how useful this technology might be in detecting and preventing crime.

AB1471 also requires at least one other internal location for microstamping a number. Microstamping on areas other than the firing pin was not tested in this study. Based on the study's preliminary results with a .22-caliber pistol, where the code on the firing pin was transferred to the brass of the cartridge rather than the softer primer, the effectiveness of such a requirement needs further assessment, Tulleners said.

David Howitt, professor of chemical engineering and materials science at UC Davis, supervised the project.

The study was funded by a grant from the California Policy Research Center, part of the University of California Office of the President. The report has completed peer review by experts selected by the center, and a paper describing the results has been accepted and scheduled for publication in an upcoming issue of the Association of Firearm and Toolmark Examiners (AFTE) Journal.

Source: UC Davis

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madrocketscientist
4.3 / 5 (3) May 13, 2008
"Codes engraved on the face of the firing pin could easily be removed with household tools, Beddow found."

That statement demonstrates the reason that mandating such technology is useless. The only reason I could see for mandating it was to assist in ID'ing casings fired by police to better understand what happens in a shooting. I could also see it as an option for concerned gun owners to have, so should their firearm get stolen, they could let officers know the engraved code, and if the person who stole it does not know it has that feature and never removes it, it could possibly lead to an arrest.

fuchikoma
5 / 5 (1) May 13, 2008
As a fully legal shooter myself, I would propose an alternative, but point out that it must not be relied upon for forensic evidence neccesarily:

A small, long-lasting engraving could be put in the upper section of the chamber near the neck of the shell casing. Depending on the caliber and ammunition, the case will naturally expand a bit and take a readable print, while putting very little wear on the stamping surface.

HOWEVER, sport shooters like myself, and some more serious hunters load or reload their old brass, even multiple times, so a criminal could collect some brass I missed from a range, load it, use it in a crime and the police would come after me first, finding my serial number stamped on a case 3-4 times. If they did not rely on this too heavily though, I would not be opposed to it - many guns will put at least reasonably unique markings on bullets from the barrel rifling, the brass from the chamber, and extractor claw, and the primer (fully removed when reloading bullets) from the firing pin and breechface/firing pin channel.
SDMike
5 / 5 (1) May 13, 2008
Another feel good law affecting only the law abiding having zero effect on criminals who, according to the US supreme court can not be forced to purchase/use/posses or be tried for failure to use such firearms. Further, most criminals who use guns are prohibited from possessing firearms due to previous convictions and can not purchase firearms anyway. Criminals or the intelligent owner about to become a criminal will simply change firing pins, use the weapon, and reinstall the engraved firing pin. Will it now become illegal to replace a firing pin? Isn't it already illegal to shoot a person? Once again liberal idiots are attacking the tool not the tool user. (I'd also install a cartridge catcher on my weapon before I went on my rampage.) Go to the range and pick up brass to throw down at the crime scene. I can think dozens of ways to defeat, hack, misuse, misdirect, spoof, this technology.
tlfiii
5 / 5 (1) May 13, 2008
Perhaps some of us who are old timers would just use a revolver and leave no brass at the scene.

Perhaps we should pass a law that a shooter must leave a note on his victim with his name and address like you are supposed to do if you hit a parked car that is not occupied.
Arthur_Dent
5 / 5 (1) May 14, 2008
There are several faulty assumptions, apparently, embodied in this enacted-law:

1. that the marking must be absolutely unique, to be *useful*
2. that the easily swapped-out or sanded-down firing-pin is the place to put the marking
3. that it must be absolutely-pervasive ( all guns, not some guns ) to be useful

If there are, say, 300 000 000 firearms in the US of A, &
each one of 'em is marked with 3 symbols ( not just a letter-number pair ),
and there are ( e.g. ) 42 possible "numerals" in the symbol-set,
then each 3-symbol mark would have only 4k possible matches ( out of 300M ), not hundreds of millions,
even not counting the further sorting of What Kind of Firearm? question.

Obviously, combination of model code would narrow it down even better.

That narrowing would be quite useful for making certain that the not-*possibly*-guilty weren't prosecuted.

And, if 50% of 'em have lasered-in markings in their chamber,
then that /does/ reduce, significantly, the number of matches,
for a found casing, even if it isn't in every single firearm.

Again, it'd do more to /protect the innocent/, than to convict the guilty.

If they want a system to guarantee conviction, then they're looking at
a) marking the inside of every chamber, &
b) chemically-marking the gunpowders ( already done, TTBOMK ), &
c) chemically-marking the bullets

( remember when investigation discovered that the FBI had known for ages that its prosecutions were basing their arguments on bogus "science",
asserting that the difference between lead-batches was guaranteed identifiable,
when in fact the chemical difference between the beginning and the end of a single batch was greater than the diff between 2 batches?
those who define their success by *enforcing* have no place claiming "justice", which requires equal forbearance & enforcing: balancing between. )

Cheers
Zig158
4 / 5 (1) May 14, 2008
Some one has been watching too much CSI. Gun chambers are not fingerprints. The article says that the markings are heavily worn at 2,500 rounds. That is nothing. It is not unusual to go to a range and put 250 to 500 rounds through a gun. At that rate it does not take long to ware off the markings. Guns are not like cars, when I buy a gun I expect to give it to my children when I'm too old to use it. There is no reason a decent gunsmith can't make this happen.
drel
5 / 5 (1) May 14, 2008
I just want to scream when governments pass laws requiring a technological solution that does not currently exist. Their idea being that if they require it, then the scientists and engineers will find a solution. That way the politicians get to claim credit for the solution.
This is just another example of legislators passing a feel good law. They can now tell their constituents that they have done something to protect the citizens. Truth be told all they have done is added to the bureaucracy. What happens when the criminal's gun (due to wear) fails to mark the case? 'The case could not have come from my clients gun.' Sounds like reasonable doubt to me'.

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