Stability of lip-print patterns: a longitudinal study of Saudi females.

Lip-print groove patterns have recently been verified as a unique parameter for identification. This study investigated the stability of lip-print patterns over time to validate their secure use in civil and criminal investigations. One hundred and sixteen female lip prints were analyzed and compared with the prints of the same subjects taken 3 years earlier. The old and new lower lip prints of each subject were examined for similarities in the groove patterns in different areas of the lip (lower right, lower middle and lower left), and a score for similarity was developed for the statistical analysis of the lower lip stability data. No significant difference in the frequency of pattern types was detected between old and new prints (P > 0.05). Statistically, 89.6% of subjects showed characteristic typical groove(s) in the lip area(s) of the old and corresponding new prints: 24.1% in the three areas, 48.3% in two areas and 17.2% in one area. This study proves the lasting stability of lip-print patterns over the years in Saudi females and recommends paying attention to the presence of characteristic typical grooves in these prints. Further studies on larger samples, including male prints, should be performed to validate the lip prints for criminal use.