First of all, the reason for gun buy-back programs isn’t “to get guns off the streets”–I doubt gangbangers and for-hire contract killers are raring to turn in their guns for a couple hundred bucks–but rather to give politicians the appearance of “doing something about crime” and the resultant media images of piles of guns, most of which are neglected, nonfunctional, or obsolete. I defy anyone to demonstrate the effectiveness of gun buy-backs in any kind of causal link to crime reduction.
Second, unless there is some reason to perform a ballistics test on a particular gun they won’t do so. Remembering from a few years ago when I was tangentially involved in forensic science (research for an abortive fiction story) I recall a standard ballistics test running about $400; for your four C’s you got a selection of bullets fired into a bullet trap, photographs and description–more on this in a minute–of the rifling marks, and a ~5 page report (most of which details the parameters under which the test rounds were fired and the condition of the gun). Costs may vary, but I doubt they’ve gotten cheaper.
Also, because there is no universally systemized way of describing rifling marks, there is no universal database to reference; you basically have to compare an evidence bullet to a test round. Cop shows, except for the rare exception like Law & Order, tend to offer the impression that rifling marks are an indelible characteristic of a gun and that bullets are always recovered intact. In fact, matching rifling marks, even with an intact round, is as much art as science, and bullets that strike a hard surface, soft lead bullets like wadcutters, or jacketed hollowpoint rounds (JHP) may often be too deformed or shed their jackets rendering them useless for detail comparison. Also, rifling characteristics will change with time, so a gun that is fired often will display different wear patterns over its lifespan. Also, barrels that are hammer forged with polygonal rifling, like the Glock or modern HK barrels, are so consistent that it may be impossible, especially with an out-of-box gun, to distinguish between like pistols.
Another thing to note, and perhaps one of our jurist members can speak in greater detail and with more authority on the matter[sup]*[/sup], but once the firearm has been accepted anonymously the chain of custody is broken. Because it (at least theoretically) can’t be traced back through its entire line of ownership back to the hypothetical crime, the issue of who possessed the weapon when is in question. For instance, the police find that a Beretta 92F, purchased by Alfred P. Bumblethumb in 1998, was used to hold up Last Chance Liquors in 2003, and turned in to the Bronx Photo-Op Gun Buyback Blowout in 2006. Now, Sammy “The Squeeze” Salviato was convicted for robbing Bumblethumb’s house in 2002, during which the pistol was stolen, and reports having sold it to inverterate liquor store robber Jimmy “Born To Lose” Bumpo just prior to the robbery, so the cops go and pick up Mr. Bumpo. Our Born Loser, an experienced veteran of the penal system, screams for his lawyer, and even the most dripping-wet-behind-the-ears Legal Aid counsellor from a third-tier law school knows that all he has to do is go before a judge and challenge the integrity of the evidence chain; lacking any way to establish ownership at the time of the crime, the evidence and all theories pertaining thereto will be inadmissable. Even if someone later steps forward and admits to having turned in the gun, the fact that it entered police receivership without a documented chain will likely result in it being found inadmissable, and our friend Jimmy released on the street to be shot by some more proactive liquor store holders. (Note to prospective liquor hold-up men: robbing a store called "Bill Hickock’s Wild West Wine and Spirits is ill-advised from both a career advancement and health & welfare standpoint.)
So, from a procedural point of view, it’s better to have a firearm that has been used in a crime “on the street”, i.e. in the hands of a criminal who can be persuaded to vouch for the trail of ownership of the gun rather than anonymously tossed in a bin. From a practical point of view, only a fraction of a percent of firearms in public ownership are ever used in a crime, and for those turned in there are plenty more to be had by theft, grift, the shady market, et cetera. Gun buy-backs look impressive but are scarcely more effective at reducing crime than is emptying a desert by shoveling sand with a pitchfork.
As far as police picking up the guns that are intended to be destroyed, well…I’m sure many are just looking for free swag and a fun plinker, but I’m guessing that this technically violates most state laws (even in states where registration of sales isn’t enforced, it is generally required that private handgun transfers be recorded by the parties) and would almost certainly violate law if the gun happens to have been transferred across state lines, interstate commerce of firearms being regulated by the Treasury Department. I would suspect that the less shiny of the law enforcement profession might use the opportunity to pick up a few “drop pieces” to be used as insurance in the case of an unjustified shooting. No doubt this occurs anyway–it’s not infrequently the case that “destroyed evidence” turns up later in the hands of a peace officer–but this seems like a wholesale encouragement of it. And again, the chain of ownership having been broken, it’s going to be difficult to tie the gun back to someone. A gun used in a questionable police shooting that could have been picked up by any of a dozen or more police officers is scarcely more evidence than a gun with no history at all.
So, in short, gun buy-back programs are at best a useless waste of taxpayers’ money, and at worst counterproductive in finding evidence and prosecuting standing crimes.
Stranger
[sup]*[/sup]I reserve the right to back-pedal and weasel to the best of my ability if and when one of our barred members comes up with an authoritative rebuttle of my claim.