New Technique for Firearms Prints

[L.J.Steele]

Scientists have developed a better way to identify fingerprints on bullets and fragments of explosives."

http://www.technologyreview.com/Infotec ... d=1316&a=f

[Veronica Rauch]

In the past, I've come across ridge detail on a casing that simply would not lift and was difficult to photograph. The resulting image did it very little justice. It did appear to be "etched" into the casing. Our agency just sent out some cartridge casings from a cold case this morning. Apparently, Dr. Bond only has one case ahead of us. Keeping our fingers crossed! Sherlock Holmes would be proud!

[L.J.Steele]

Anyone know how long these images last? If, for example, one has a reloaded casing that may have been handled by several prior owners, reloaders, packers, etc -- which show up?

[Veronica Rauch]

It's to my understanding, that once the projectile is fired, the moisture components left behind from the fingerprint residues are permanently "etched" into the casing. Unfortunately, following conventional processing techniques which failed to develop anything, our casings were handled by ungloved firearm personnel. So, it's quite possible we might be looking at their prints instead.

: (

[L.J.Steele]

The Boston Globe has a story on this:

http://www.boston.com/news/science/arti ... ky_fingers

Anyone familiar enough with the research to comment on issues of cross-contamination and age of prints? There's been a running debate in GSR testing about false positives caused by arresting officers who may have recently fired their weapons, or even taking suspects thru sally ports that happen to be located in garages near where the firing range vents come out.

I know there's been litigation about the trace amounts of narcotics found on much US currency -- is there a similar problem with trying to pick up traces in prints?

[antonroland]

I understand the concern for age of prints being a factor if we talk about a can of baked beans on a supermarket shelf but are there really that many exculpatory explanations if a print is found on a cartridge case?

[L.J.Steele]

I understand the concern for age of prints being a factor if we talk about a can of baked beans on a supermarket shelf but are there really that many exculpatory explanations if a print is found on a cartridge case?

Yes, in a sense. Let's take a gang shooting. Police are pretty sure that a member of the Island Brothers shot a member of the Ghetto Brothers. There's a hefty amount of brass left at the scene. If merely handling the ammo can generate prints,they could come from the shooter, or at least the guy that loaded the gun the last time. Or they could come from any of the guys who were admiring the weapon at some point in the past, manipulating the slide, putting back the bullet they extracted doing that, posing with it and the ammo for a Facebook picture (yup, some of them are dumb enough to pose with illegal guns and post it), or the guy who's got a rep as good with his hands who was asked to check out or repair the gun, or the hanger-on who helped get the gun and some loose ammo around a security check at a club, or the younger sibling who was messing with his gangbanger brother's gun.

It does show the person handled the object and might be great for an illegal possession charge. The problem is going to come when the prosecutor wants to use it to show the person who's print it is was the shooter.

I'm still wondering how this works on reloaded ammo. The stuff I use for target practice is commercially reloaded -- so been handled by lots of hands from the manufacturer to the original shooter to the reloader to me, and possibly several iterations of shooter and reloader depending on the age of the brass. I'd expect the tumbling process to clean the brass would take off most marks, but does anyone know?

[antonroland]

As a combat pistol marksman and advanced reloader of more than a decade I think I am qualified to answer that question.

Tumbling of cases inbetween loading should remove all but the most hardy of finger prints. The only fingerprints I have ever found on cases to survive the tumbling and reloading process were ( I assume very acidic) prints that were in an advanced state of chemical etching into the case after about six months of storage.

I bought some .40 S&W brass off a friend - they are hard to come by and pricey down here - and discovered the ugly reddish brown finger marks etched into the metal after storage when I started loading them. No amount of time in the tumbler would remove the marks although they were less noticeable. (I used fresh batches of Lyman's corn cob green)

I would say about 20-30% of the marks contained very clear third level in parts but most were rather smudged and of no value for identification purposes.

Any meticulous reloader would also clean the loaded cartridges after the loading process is complete and should thereby remove justabout all prints but his own.

I have heard of guys (THIS IS NOT A GOOD IDEA) who clean their freshly loaded ammo in a short tumbling run. Now I must confess to have done this myself with military issue / carry ammo when it became old but there is always the unlikely event of something going horribly wrong...small but possible.

I think the implications on prints older than the reloading process becomes clear...

Hope this helps.



PS and more to the point made by the previous poster...surely there is always further investigation into the forensic findings and investigation is not substituted by a rush for the courthouse, right?