Fingerprints' third dimension: the depth and shape of fingerprints penetration into paper--cross section examination by fluorescence microscopy.

In an attempt to maximize the yield of latent fingerprints from paper items, we conducted a study of a fundamental process between fingerprint deposits and paper. Fingerprint ridges have been observed in the cross section of paper by fluorescence microscopy. It was possible to see, for the first time, how residue from fingerprint ridges is embedded in paper. Undeveloped, latent fingerprints, as well as latent prints developed by the two fluorogenic reagents, DFO and 1,2-indanedione, have been examined. The shape and depth of penetration of fingerprints vary with different types of paper. An inverse relationship between the smoothness of the paper and the penetration depth was observed: higher smoothness values result in lower depths of penetration. High quality prints appear to correlate with an optimal penetration depth-between 40 and 60 microns.