Colour quantitation for chemical spot tests for a controlled substances presumptive test database

Area of Science:

• Forensic Science
• Analytical Chemistry
• Digital Forensics

Background:

• Crime scene investigators (CSIs) frequently encounter unknown substances, including controlled drugs.
• Visual identification of white powders is challenging, and colorimetric tests can yield subjective results.
• Variations in color perception and environmental conditions affect the reliability of traditional presumptive drug tests.

Purpose of the Study:

• To evaluate the utility of smartphone applications for quantitative reporting of colorimetric drug tests.
• To establish a standardized, objective method for recording presumptive drug identification results.
• To develop a comprehensive digital library of drug test results for field use.

Main Methods:

• Two state-of-the-art apps, ColorAssist® and Colorimeter®, were tested for reporting colorimetric results in RGB format.
• A large database of over 3300 data points, including 800+ drug/test combinations, was compiled.
• Variations were analyzed based on test replicates, different days, device types, and drug quantities.

Main Results:

• ColorAssist® with camera light showed the least variation (Euclidean norm 25.1±22.1).
• Variations between replicates and across different devices were comparable.
• The study quantified the reliability and consistency of app-based colorimetric analysis.

Conclusions:

• Smartphone applications offer a promising solution for objective and uniform reporting of presumptive drug test results.
• The developed RGB library enhances the identification and interpretation of controlled substances in forensic investigations.
• Digital tools can significantly improve the accuracy and consistency of field drug testing.