Shape Variations in Loop Pattern Fingerprints: Radial vs. Ulnar Loops

Loops are very common categories of fingerprint patterns found on terminal phalanges of the human hand. Their assessment is paramount in the process of police fingerprint identification. A detailed classification system capable of distinguishing between radial and ulnar loops, loops of right and left hand, or those of thumb and other fingers would largely benefit to cases where only a single loop is secured at crime scene. The aim of our pilot study was to assess differences in size and shape of radial and ulnar loops. We explored morphological variations in the sample of 489 loop ink fingerprints using 20 distance measurements and indices and Fourier shape analysis. Our results show that there are systematic size and shape differences between radial and ulnar loops on index fingers, primarily concentrated in the course of the distal type line. If developed further the proposed methodology, particularly if directed at advanced methods of geometric morphometrics, may find practical usage in differentiating fingerprint patterns in police/forensic fingerprint investigation.