Crystal Pattern Matching Recovers Obliterated Serial Numbers From Metal

chicksdaddy writes Criminals beware: researchers at the National Institute of Standards and Technology (NIST) have figured out how to recover serial numbers obliterated from metal surfaces such as firearms and automobiles — a common problem in forensic examinations. According to this report, NIST researchers used a technique called electron backscatter diffraction (EBSD) to read, in the crystal structure pattern, imprints on steel that had been removed by polishing. ... The more perfect the crystal structure, the stronger and clearer the pattern. Software can then calculate the pattern quality to reveal crystal damage; areas with more damage produce lower quality patterns. In the NIST experiments, described in Forensic Science International, researchers hammered the letter 'X' into a polished stainless steel plate. The letter stamps were as deep as 140 micrometers, meeting federal regulations for firearm serial numbers. The researchers then polished the metal again to remove all visible traces of the letters, and collected the EBSD diffraction patterns and pattern quality data and analyzed them for evidence of the imprints.

Comments

Overstamp First?

[theshowmecanuck]

What if you use some tool and hammer to overstamp the serial numbers. Like scribbling over it. Then grind it down. Or if it is in a place that can be heated and cooled... like annealing... where any loss in strength from the operation, were it to happen, wouldn't be an issue. Would that change the underlying crystal structure significantly. I'm sure it would affect it some, but would it be enough to allow the crystal structure to 'reset' and erase the original stamp marks?

Overstamp twice.

[Okian Warrior]

If you do it stupidly, like put a "1" through an "A", it would be fairly obvious and narrow the search down.

Punching 1 through an A leaves the firearm with two possible choices in that digit. Do this for 9 digits, and you get 2^9 = 512 possibilities. Punch twice through each digit and you get 3^9 possibilities.

In fact, punch *all* the digits in each position, then file it down.

This will rapidly be entered into the "big book of best practices" for criminals.

And it's also a moot point, since easy access to guns reduces crime, and it's likely that 3-d printed guns will be easily available in the next decade or so.

(And so what if the 3-d printed gun is reliable for only the first couple or shots? That only means that you use your 3-d printed gun that took 2 hours to print and $3 to build a couple of times and then melt it down.)

Re:Overstamp twice.

[Anonymous Coward]

This will rapidly be entered into the "big book of best practices" for criminals.

And it's also a moot point, since easy access to guns reduces crime, and it's likely that 3-d printed guns will be easily available in the next decade or so.

Criminals are pretty notorious for not following "best practices". A majority of violent criminals suffers from ADHD and acts without thinking. It is unlikely that the few that thinks about getting rid of the serial number are bright enough to know about technologies like this.
As for easy access to guns reducing crime that sound like bullshit propaganda to me, do you have a credible source for that?

Millions of dollars in research.

[He Who Has No Name]

Defeated by a $59 Dremel tool that completely removes the metal from that area of the frame...

Re:3D print the gun,

[Anonymous Coward]

Removing markings from metal is an easy process that can be done with hand tools and power tools. If you were to remove all of the metal behind the markings i would expect the analysis to fail.
A polymer gun is easier, as you only have to grind off the metal plate holding the markings and are still left with an intact tool.
Creating a working gun, or the part of the gun that requires a serial number is not easy. You can try to use a 3D printer, a CnC Mill or in come cases, like the AK-47, a shovel and hammer. It is not easy.
You now have to procure the rest of the weapon and assemble it. Purchasing lots of parts that should fit, usually do not. If someone has the time, intelligence, resources and skills required to make a gun, they can use those four things to build far worse things. Someone shooting up a mall is going to yield fewer casualties than someone blowing up a large portion of it or releasing poisonous gas into an enclosed space.
Crying wolf with 3D printing did wonders for ratings but it's not putting guns into the hands of criminals. A pipe and a nail, steel and a welder, the black market, are all much easier methods to procure a gun. A quick look at prisoners and oppressed cultures shows how easy it can be to make a weapon. 3D printing isn't one of them.

If you happen to have access to something awesome like a metal or commercial plastics (much stronger than PLA and ABS) 3D printer, please use it. If you do make a gun and are worried, you can always add your own markings and register it.

Ok, what about recrystalization?

[wierd_w]

Metal grain boundries change if you heat the metal up. This also removes the temper, but rapid heating followed by rapid cooling (Such as by very high speed friction sanding, then submersion in water or oil) will change the crystal grain structure of the metal pretty deeply if done right.

Failing that, sanding off the top layer, then applying heat with a heat gun for a few minutes, then clenching with a cold oil pour will have the same effect, but more reliably.

Seriously, this is how heat treatment of steels works. Steels and other metal alloys go through various phases of crystal growth types under different temperature and pressure environments. They grow when hot (but not molten) which is why the metal weakens. If you heat it up hot enough, this processes changes into annealing where the crystals break down from thermal forces and the metal becomes amorphous. Flash cooling results in a densely packed matrix of tiny metal grains, which strengthens the metal.

Seriously-- all you have to do is alter the crystal growth pattern under where the serial number was. Heat treatment will do exactly that.

Could Be Handy in the Gun Shop

[CanHasDIY]

This could actually be useful for gun shops, since we have to meticulously catalog the serial numbers of all firearms that come in and go out. We often get older (like, 150 year older), used firearms where the serials are worn down and difficult to read, even with a jewelers loupe.

Or rather it would be useful for gun shops, if the process isn't as cost-prohibitive as I presume it will be.