Visualization of methamphetamine-contaminated fingermarks on glass surfaces by field emission scanning electron microscope for forensic investigation

Background: Fingermark is an individual's primary identification source. It is helpful in determining individuals involved in illegal activities and is frequently encountered in clandestine laboratories. During forensic investigation, the critical question to be answered is whether a fingermark was left on a surface before or after the initiation of an unlawful activity. Aims and Objectives: This study aimed to investigate the visualization of methamphetamine-contaminated fingermarks on glass surfaces and estimate the immediacy of their depositions. Materials and Methods: In this study, the prior-deposition contaminated fingermarks, i.e., fingermarks deposited a surface priorly contaminated by methamphetamine, and the postdeposition contaminated fingermarks, i.e., fingermarks deposited on a clean surface but subsequently contaminated with methamphetamine were visualized and compared using Field Emission Scanning Electron Microscope (FESEM). Results: Under FESEM, the latent fingermarks and the crystalline structure of methamphetamine were clearly visualized. The postdeposition contaminated fingermarks appeared in smudge conditions in all the three replicate samples, where the ridge and nonridge areas could not be well-distinguished. On the contrary, the prior-deposition contaminated fingermark demonstrated distinct separations between ridges and nonridges. However, the application of fingerprint powders reduced the possibility to determine the immediacy of deposition. Conclusion: To conclude, both prior-deposition contaminated fingermarks and postdeposition contaminated fingermarks can be discriminated, providing information on the instance when a fingermark was left on a surface.