CPRC in the Sunday Washington Post: “Maryland’s long-overdue goodbye to ballistic fingerprinting”

John Lott’s op-ed at the Washington Post starts this way:

Ballistic fingerprinting was all the rage 15 years ago. Maryland led the way, setting up a computer database on new guns and the markings they made on bullets. New York soon followed. The days of criminal gun use were supposedly numbered.

It didn’t work.

The registration of ballistic fingerprints never solved a single crime in Maryland or New York. New York scrapped its program in 2012. This month, Maryland announced it was following suit.

Maryland spent $5 million on its computer database. By 2005, New York was spending about $5 million per year, showing that even greater per-capita spending didn’t guarantee success.

Think of all the other police activities that this money could have funded. How many more police officers could have been hired? How many more crimes solved?

It has long been clear that these states’ programs weren’t working. A 2005 report by the Maryland State Police’s Forensic Sciences Division labeled the operation “ineffective and expensive.” Similar statements by police have been ignored for years.

Gun-control advocates predicted the success of ballistic fingerprinting. For example, Dan Webster of Johns Hopkins’s Bloomberg School of Public Health argued that the vast majority of criminals obtain their guns legally. Authorities, he predicted, would be able to establish matches between firearms in the database and spent rounds found at crime scenes.

Webster was wrong on both counts. Very few criminals legally purchase guns. Recording the markings on guns was a waste of time and money.

But gun-control advocates ignored physics. When a bullet travels through the gun barrel, the friction creates markings on the bullet. If the gun is new, imperfections in the way the barrel is drilled can produce different markings on the bullet; such imperfections are most noticeable in inexpensive guns. In older guns, the bullet’s friction through the barrel can cause more noticeable wear marks that help differentiate between guns. Many other factors influence the particular markings left on the bullets — for instance, how often the gun is cleaned and what brand of cartridge is used.

Unlike human fingerprints and DNA, a gun’s ballistic fingerprint changes over time because of wear. A child’s fingerprint can still be used much later in life. A ballistic fingerprint, on the other hand, is more like the tread on a car tire. New tires of the same brand and model, with minor exceptions, are essentially identical. Over time, though, friction causes the tread on tires to wear. The more the car is driven after the crime, the harder it is to match the tire tracks left at the scene to the tires when they are eventually found.

The same is true for guns. The greatest friction on a gun occurs when the gun is first fired — and that dramatically and quickly reduces the usefulness of recording the gun’s ballistic fingerprint when it is purchased.

Criminals can thwart ballistic fingerprinting by replacing the barrel of a gun. They can alter the ballistic fingerprint by just scratching the inside of the barrel.

The response from gun-control advocates: Fifteen years and $5 million weren’t enough. They simply need more time because the science is valid. They claim that, on average, most guns used in crimes were bought nearly 15 years prior. But even if that were accurate, it wouldn’t explain why the systems in Maryland and New York haven’t solved one crime.

People should be held accountable for their predictions. The only thing the program accomplished was making it more costly to legally sell guns.

Good intentions don’t necessarily make for good laws. What counts is whether the laws save lives. On that measure, ballistic fingerprinting is just another failure in a long line of failed gun-control measures.

The piece is available here.

UPDATE: Dan Webster had a letter to the editor on November 20th.

John R. Lott Jr.’s Nov. 15 Local Opinions essay, “Goodbye to ballistic fingerprinting,” claimed that I contend that most criminals obtain their guns legally. Data from a national survey of state prison inmates indicate that about 40 percent of gun-crime offenders were not legally prohibited from having guns when they committed the crime leading to their incarceration. The share of offenders who legally possessed guns grows to 60 percent in states with the weakest legal standards for gun ownership. Among gun offenders barred from possessing guns, 82 percent obtained a gun through private transfer. In the majority of these transactions, the seller is not violating the law because of gaps in background-check laws.

It seems clear that Mr. Webster concedes that Lott’s “contention” is correct.  The issue here for whether the ballistic fingerprinting works is whether the guns were legally purchased so that the ballistic fingerprints would be recorded.  The irony is that Maryland has had universal background checks since 1996 (in New York since 1977).  If guns aren’t in their data set, it isn’t because they didn’t go through legal background checks, which means that they were obtained illegally.  The survey of state prison inmates has only 40 percent of guns were obtained from friends or family, but not whether the criminals went through a background checks to get those guns.

If most guns used in crimes were obtained legally, in the Maryland or New York they would be in the data base.  But either these guns weren’t in the data base or the markings had changed from the time the guns were first recorded.  Yet, the data base solved zero crimes.

Mr. Lott suggested that gun laws don’t affect criminal acquisition and use of guns. This is contradicted by research showing that when legal standards for gun ownership are raised, violence by the affected groups is reduced. My research has shown that extending background-check requirements to all handgun sales, especially when accompanied by purchase permits, reduces the diversion of guns to criminals and homicides committed with guns. These truths are inconvenient for Mr. Lott, who advocates for fewer restrictions on gun access.

What Lott believes is that gun laws tend to have a bigger impact on law abiding individuals than criminals.  This was not part of the discussion in his op-ed and the fact that Webster spends so much of his letter gives him virtually no space to respond to the longest discussion about the physics of ballistic fingerprinting.

Webster cites his work on Connecticut and Missouri claiming that background checks and licensing stop violent crime as evidence that these criminals had previously been obtaining their guns from legal sources.  A discussion of those two studies are available for Connecticut is available here and for Missouri here.

Mr. Lott argued that Maryland’s law requiring state police to log ballistic images from casings fired by handguns sold in the state was inconsistent with science. Yet for decades, detectives have been solving cases using ballistic evidence and computer software to read and match images.

So why was Webster so wrong about whether the program would succeed?  The point of the piece is that the markings made on bullets change particularly quickly when guns are new.  No rebuttal is offered for that point.  Even for the general reference to detectives solving cases, there is a lot of art in making these comparisons.