New Forensic Study Explores How Fingertip and Nail Shapes Could Help Identify Suspects

A new forensic study has examined whether the three-dimensional shapes of fingertips and fingernails could help investigators compare hands captured in crime-scene photographs and videos with those of potential suspects.

Published on November 5, 2026, in Scientific Reports, the research was conducted by Kazuhiko Imaizumi and Shiori Usui of Japan's National Research Institute of Police Science.

Hand comparison can become important in sexual abuse investigations when photographs or recordings show a person's hands but not their face. Investigators may examine finger proportions, nail shapes, and other visible characteristics to assess whether two images could show the same individual.

However, the scientific evidence supporting such comparisons remains limited.

To address this problem, the researchers examined three-dimensional fingertip and nail shapes using statistical techniques, including principal component analysis.

This approach identifies patterns of variation across multiple measurements rather than relying entirely on subjective visual judgments.

The study identified several important differences in fingertip morphology, including variations between broad and narrow fingertips, the relative area occupied by nails, and how deeply nails appear embedded in surrounding tissue.

Nail shapes also varied in width, curvature, and projection.

The researchers additionally measured finger-segment lengths and identified relationships between corresponding segments across different digits.

These findings provide reference information that could support future research into forensic hand comparison.

However, identifying measurable anatomical differences does not establish that a particular hand shape is unique to one person.

The study does not demonstrate that investigators can reliably identify suspects from fingertip or nail shape alone.

Image quality, camera perspective, hand positioning, and differences between populations may also affect comparisons.

The research contributes to efforts to establish a stronger scientific foundation for forensic image examination, particularly in cases where conventional facial or fingerprint evidence is unavailable.