The National Research Council have published a report advising against a national database of “unique” markings made by firearms on bullets and brass.

“Ballistics testing is only as useful as the number of images in the database,” Sen. Herb Kohl, D-Wis., said while pushing for the database in 2002.

Actually, the opposite is true, today’s report said. The larger the database, the more errors the computer will return.

Under the current system, the computer might find 10 possible matches for a single bullet and there’s a good chance one of them will be confirmed. After adding more than 1 million guns to the database each year, the same system might produce hundreds of possible matches.

Comparing rimfire brass. Photo from forensicmag.com.

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