Examination of the steps leading up to the physical developer process for developing fingerprints

Area of Science:

• Forensic Science
• Chemistry

Background:

• Latent fingerprint development often involves physical developer treatment.
• Paper substrates frequently contain calcium carbonate, which can interfere with physical development.
• Acid prewashes are commonly used to neutralize calcium carbonate before physical development.

Purpose of the Study:

• To systematically evaluate the effectiveness of various acid prewashes and water rinses on paper for latent print enhancement.
• To determine the optimal acid type, concentration, and duration for pre-treatment.
• To assess the necessity of a water rinse step prior to physical development.

Main Methods:

• Testing two different acids (malic and citric) at varying concentrations and wash times.
• Examining multiple paper types to assess prewash efficacy.
• Conducting a pH study to monitor solution acidity during washing.
• Utilizing scanning electron microscopy to quantify surface calcium levels on paper samples.

Main Results:

• A 2.5% malic acid prewash demonstrated optimal performance across most paper types.
• This concentration provided excellent latent fingerprint development with minimal background interference.
• Water rinses prior to physical development were found to be unnecessary and did not improve results.

Conclusions:

• Malic acid at 2.5% is recommended as an effective pre-treatment for latent fingerprint development on paper using silver physical developer.
• Eliminating the water rinse step can streamline the forensic analysis process.
• Understanding paper chemistry is crucial for optimizing forensic techniques.