Visualizing shed skin cells in fingerprint residue using dark-field microscopy

Area of Science:

• Forensic science
• Biomolecular imaging

Background:

• Fingerprint analysis often relies on ridge patterns.
• Cellular material within fingerprints offers additional forensic information.
• High sebum content in fingerprints can obscure cellular details.

Purpose of the Study:

• To evaluate dark-field microscopy for visualizing cells in high-sebum fingerprints.
• To quantify cellular deposition and transfer dynamics on smooth surfaces.
• To explore plasma etching as a method for enhancing cell visualization.

Main Methods:

• Dark-field microscopy was used to image cells in fingerprint residue on polyethylene terephthalate (PET).
• Cell transfer was measured across repeated skin contacts under controlled force.
• Plasma etching was investigated for sebum removal to aid microscopy.

Main Results:

• Dark-field microscopy provided sufficient contrast for cell visualization in fingerprints.
• Cell transfer decreased exponentially with repeated contact, reaching a steady state of 78 ± 36 cells.
• Plasma etching effectively reduced sebum while preserving cell integrity for microscopy.

Conclusions:

• Dark-field microscopy is a viable technique for visualizing and quantifying cells in fingerprints on smooth, non-light-scattering surfaces.
• Understanding cell transfer dynamics is crucial for forensic applications.
• Plasma etching offers a complementary method for sample preparation in cell-based fingerprint analysis.