Popular crime dramas lead many to believe it's easy to confirm a person's identity from a fingerprint. In reality, it's not so simple. A number of factors make identification difficult: whether information has been entered into a specific database, if the specimen is smudged or a partial print, and if that print has been altered.

An app for that

Very little research has been done in this last category. Existing software can alert law enforcement if the print image quality is poor. But that isn't much help because many altered prints are of good quality.

Fugitive William Keegan had all 10 fingers surgically altered in the 1990's to obliterate his fingerprints above the first joint.

Jain's graduate student, Soweon Yoon, was part of a team that designed a precise algorithm that helps software systems identify altered prints.

“The most important feature for fingerprint matching is called minutiae. So minutiae refers to [a] ridge ending point and [a] ridge bifurcation point," Yoon says. "From typical fingerprint impression, we can extract 100 minutiae per each finger.”

While patterns on most of our fingers flow in curves and loops, those who have altered fingerprints have abrupt, discontinued lines. That generates an unusually high number of minutiae points.

“You can imagine if someone makes a cut here, they will generate a lot of ridge ending points, so that generates [an] excessive number of minutiae,” Yoon says.