Solvent-free method for developing latent fingerprints by applying superfine ninhydrin powder.

Area of Science:

• Forensic Science
• Analytical Chemistry
• Material Science

Background:

• Ninhydrin is a standard reagent for developing latent fingerprints on porous materials.
• Traditional ninhydrin solutions can damage inks and cause thermal paper to darken.
• Existing methods require pre-prepared solutions, increasing costs and potential hazards.

Purpose of the Study:

• To introduce and evaluate a novel solvent-free method for fingerprint development using superfine ninhydrin powder (ASNP).
• To compare the efficacy of the ASNP method against traditional ninhydrin solutions.
• To assess the ASNP method's performance on diverse paper types, including challenging substrates like thermal and carbonless copy paper.

Main Methods:

• Direct application of finely ground ninhydrin powder to paper surfaces.
• Controlled heating and humidification to promote ninhydrin diffusion into paper fibers.
• Comparative analysis of ASNP and traditional ninhydrin methods under varying temperature and humidity conditions (60°C/40% RH and 50°C/65% RH).

Main Results:

• The ASNP method, particularly at 50°C and 65% RH, significantly improved fingerprint visibility, with prints appearing within 6 hours.
• After 24 hours, the ASNP method's performance was comparable to the traditional ninhydrin solution.
• The ASNP technique demonstrated effectiveness on various paper types, including thermal and carbonless copy paper, with minimal background staining.

Conclusions:

• The solvent-free ASNP method presents a viable and advantageous alternative to traditional ninhydrin solutions for latent fingerprint development.
• This technique eliminates the need for solution preparation, reduces costs, and mitigates solvent-related damage and environmental concerns.
• ASNP is particularly effective for developing fingerprints on sensitive materials like thermal and carbonless copy paper.