Saturday, February 07, 2004

In an interesting development, I'm almost inclined to believe that ballistic fingerprinting could be theoretically as accurate as biometric fingerprinting.

"...At present, there is virtually no accurate information on just how often fingerprint examiners actually make mistakes -- and unlike DNA experts, fingerprint experts routinely testify that their matches are '100 percent certain'."

Hmmm. I see the parallel between biometric fingerprint examiners & the BATF already. Here's a quote from BATF agent Thomas A. Busey (actually he was Chief of the National Firearms Act Branch of the BATF when he made the statement)

"...when we testify in court, we testify that the data base is 100% accurate. That's what we testify to, and we will always testify to that. As you probably well know, that may not be 100 percent true."

Nothing like a little honesty in dishonesty government. Back to the biometric fingerprint piece:

"Fingerprinting is often said to be be infallible, a forensic 'gold standard.' But if we ask how often declared fingerprint matches are actually wrong, the only honest answer is that no one has any idea...There are no systematic proficiency tests to evaluate examiners' skill. Those tests that exist are not routinely used and are substandard. In another recent case, even the FBI's proficiency tests were acknowledged by another fingerprint examiner to be absurdly easy."

Sounds as if they've taken the scientific approach that many gun control advocates use. Say you're right about a subject, but fail to provide any credible documentation to back your claims. But be sure to label someone an "expert" if they agree with your claim, despite their qualifications.

"...there are no uniform standards, locally or nationally, about what counts as a fingerprint match. Different jurisdictions, and even different examiners, have different criteria, and the courts have simply left it to the experts' judgment."

Again, not that different from the "assault weapons" legislation across the country.

"In addition, we have no idea how often two individuals -- whose prints would indeed look different if we had access to a complete set of 10 undistorted prints -- might have partial fingerprints that resemble each other enough for an examiner reasonably to mistake them as coming from the same person, especially when the print lifted from the crime scene might be smudged and distorted."

& similarly this is a flaw in the ballistic fingerprinting concepts that have been pushed around: the idea that a partial match is conclusive proof that the two prints came from the same source.

Here's ballistic fingerprinting in a nutshell:

Ballistic fingerprinting is suppossed to match the "unique" markings left on the projectile to the barrel that made them.

However, one must remember that the markings a barrel will leave on a projectile will change over time. A projectile of lead or any other metal travels down a steel barrel at great speed - often faster than the speed of sound. This creates friction which wears on both the projectile & the barrel. The same process that imprints markings from the barrel on the projectile wears down the barrel itself. The rate of this wear is dependent upon several variables not the least of which is projectile speed. Some cartridges are more wear intensive than others, but all cartridges cause this wear to some degree or the other. In fact, many gunsmiths could make a decent living off of rebarrelling alone. Some cartridges in common use for certain shooting sports (namely benchrest competition) will wear down the rifling in a barrel to the point that accuracy suffers because the bullet no longer tightly fits the barrel. This can happen in as little as a few hundred rounds, although most rifle cartridges will not degrade accuracy of a barrel for at least a few thousand rounds.

So the markings left by the barrel itself tend to change with use.

Another variable is intentional alteration of the barrel. A piece of No.4 steel wool run down a barrel a few times will alter a barrel enough that it cannot be matched with 100% certainty to the projectile that it shot last. A pocket knife, coat hanger or any other piece of metal can later a barrel's "unique" markings in a matter of seconds.

& this notion of matching a projectile to a barrel is further nullified when dealing with shotguns, which with a few exceptions, have no rifling at all to make a mark & typically fire shot (many projectiles) in a protective plastic cup.

Ballistic fingerprinting is completely erroneous, except as an example of how unscrupulous or ignorant politicians will use junk science to further a prejudicial goal.

Professor Jennifer L. Mnookin's article is an excellent response to those who keep insisting that ballistic fingerprinting is as accurate as biometric fingerprinting. They may in fact even be correct. Ballistic fingerprinting may be as accurate as biometric fingerprinting in certain cases. They just don't realize that those cases would be where biometric fingerprinting is as accurate as the witch dunking test abandoned in the 17th century.

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