Title

Evaluating the Ability of Different Weak Acids When Combined with Hydrogen Peroxide to Develop Latent Fingerprints on Post-Fired Cartridge Cases

Semester

Fall

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Forensic and Investigative Science

Committee Chair

Keith Morris

Committee Co-Chair

Suzanne Bell

Committee Member

Patrick Buzzini

Abstract

This study examined the effectiveness of different weak acids in developing fingerprints on different types of cartridge cases when combined with hydrogen peroxide due to a process known as chemical etching. Chemical etching involves an oxidation-reduction in which the metal is oxidized by the acid. Three types of cartridge cases were used: bi-metal, brass, and aluminum. Five different acids of varying pKa were used: acetic, citric, lactic, maleic, and propanoic. Each acid was made up to a different concentration to reflect the same pH as 1.0M H+ ions. Phase I involved testing each acid with each case printed after firing to determine which acid, in what amount, best developed the latent fingerprint. Both mV and pH were measured to determine optimum conditions for development. Two experiments involving the citric acid, adding 25mL at the beginning and adding 1mL every 3 minutes 30 times, and one experiment involving the acetic acid, adding 7mL at the beginning, were determined to produce the best quality fingerprint on brass cartridge cases. Therefore, these methods were further tested in Phase II. Phase II involved using the three methods previously described to develop a latent fingerprint on a brass cartridge case that was 'spiked' with a fingerprint before firing. Each experiment was run three times with mixed results. While no method produced consistent results, adding 25mL of the citric acid at the beginning was able produced some ridge detail on one of the three cases tested. Citric acid combined with hydrogen peroxide was shown to be an effective development method when developing fingerprints on cartridge cases.

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