NIST database goes ballistic

The ability to match a bullet with the gun that fired it has been a forensic staple for law enforcement for almost 150 years, but the National Institute of Standards and Technology is hoping to juice the old capability with 21st century big data.

NIST opened a 3D Ballistics Research Database for to law enforcement use on July 7. The new database  will provide statistical foundations using an open-source developed algorithm to more reliably link bullets to the guns that fired them.

On television cop shows, striations left on bullets are easily matched visually to the rifled grooves inside gun barrels, typically using nothing more than a microscope. In real life, however, NIST said the process is far from straightforward.

Uncertainty can make trial jurors uneasy, said Xiaoyu Alan Zheng, a mechanical engineer who conducts forensic science research at NIST. Zheng said that juries "want to know, 'How good a match is it?'"

Matches can be blurred by a number of things. Guns made at the same time may have extremely similar grooving, and an individual gun's barrel can change over time -- both of which can confuse less-sophisticated analyses.

The new database helps vastly narrow down those nuances and differences by harnessing algorithms derived from a growing library of three-dimensional images of bullets. 

Zheng told FCW in an email that NIST will host the database at its facilities, but is relying on outside sources to expand its library of bullet profiles.

To start the database, Zheng said he asked forensics and law enforcement conferences to test-fire every 9-mm firearm in their reference collection. He said that 9 mm is known to be the most commonly used in the commission of crimes. 

"NIST will continue to collect, measure and enter new test fires contributed from laboratories across the US. In addition, participating agencies will have the ability to upload data into the database themselves," Zheng said. "One of those agencies is the FBI, and we anticipate that a large portion of the database's growth will come from the FBI's firearm reference collection."

Zheng said the FBI's firearm reference collection consists of thousands of firearms, but the law enforcement agency is planning to multiply those references by a factor of six by using six different brands of ammunition per firearm to generate the test fires. "FBI will upload their measurement data onto the NBTRD as well as providing physical test fires to NIST."

According to NIST, after labs completed the test fires, they sent the bullets and cartridge cases to the agency, along with data on the gun that fired it. At NIST's lab, technicians scanned the samples using a microscope that produces a high-resolution, 3-D topographic surface map, which produces a virtual model of the physical object itself.

The surface maps produce more detailed comparison data than the two-dimensional images traditionally used to match bullets.

NIST said its new database is open access and the data in it is freely available to researchers. Similar databases already in use, such as the National Integrated Ballistics Information Network, are proprietary and contain sensitive information. Researchers can't download bulk data from other databases for use in statistical studies.

"As far as uploads are concerned, the database is secure and protocols are in place to ensure data quality control," said Zheng. When data is submitted, he said, the database administrator uses a program to check scanned data files and strip out any extraneous metadata, leaving only the 2D image or 3D topography data. Once the data is live on the server, only the database administrator has access to modify those files, said Zheng.