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Latent Fingerprint Development on Thermal Paper Using Muriatic (Hydrochloric) Acid

NCJ Number
Journal of Forensic Identification Volume: 52 Issue: 4 Dated: July/August 2002 Pages: 427-432
Beverly Broniek; Wade Knaap
Date Published
6 pages
This paper describes experiments done to determine whether exposing thermal paper to muriatic acid vapors would facilitate the development of latent fingerprints on the emulsion side.
Several samples of retail sales receipts and automated bank teller receipts were obtained from a variety of locations. These samples included white thermal paper and other types of white and colored paper receipts. A 4-liter plastic container of muriatic acid was purchased from a swimming pool supply store. Approximately 25 ml of muriatic acid was poured into a clean jar, and the jar was secured with a metal lid to contain the vapors. The metal lid was removed and the receipts were individually held over the escaping vapor. Following this process, the paper was removed and the container was resealed. Subsequent testing was conducted to ascertain the suitability of incorporating other standardized processes, including DFO and ninhydrin. These processes were conducted on the thermal paper before and after the muriatic acid fuming, in their respective order. The thermal paper that had been fumed by means of exposure to the muriatic acid vapor developed latent fingerprint impressions with remarkable first, second, and third level friction ridge detail. Generally, fingerprint impressions reached their maximum clarity within approximately 5-10 seconds of exposure to the muriatic acid vapors. Use of this technique, however, voids any other standardized development process for paper and is only viable for thermal paper, specifically the emulsion side. Caution must be used to avoid contact of the acid with the skin or inhaling the vapors. 4 figures and 4 references