Out of print

Natural History, March, 2009 by Don Cook

Olivia Judson's "Life Zone" column on fingerprints ["Sticky Fingers," 12/08-1/09] was a great story but didn't address the effects of aging. After 9/11, needing security clearance, I had a full set of fingerprints taken and filed with the FBI. But now, at the age of seventy-three and a half, my fingerprints are all but gone. My right thumb appears to have a full print, but the other digits on both hands are now virtually smooth. A senior-citizen friend of mine was denied clearance for a job, because of a lack of fingerprints. Can digital equipment still read the prints even if an ink pad doesn't register any?

Don Cook

Skokie, Illinois

OLIVIA JUDSON REPLIES: Don Cook raises an important point that has been generally overlooked in the scientific literature. However, a recent report on biometrics commissioned by the British government did note the difficulty in obtaining high-quality fingerprints from the elderly--and suggested that identification schemes should take that into account. Three factors appear to contribute to making fingerprints more difficult to read as one ages. The first is that the skin smoothes--because skin cells are no longer replaced quickly enough to keep up with wear--decreasing the contrast between ridges and valleys. The second is that wrinkles in the skin add noise to the print that is obtained. A third factor is a drop in fingerprint moisture. To my knowledge, digital readers can't resurrect ridges and valleys. Various computer algorithms, though, have been developed to try to filter out the noise from wrinkles, and also to enhance any remaining attributes of a fingerprint.