The lanthanides are a subset of the rare earth elements; their emission of light has been of interest for a long time in many scientific and technical fields. The lanthanide-based method was used to test samples designed to simulate counterfeiting. Most of the research has been confined to fresh fingerprints due to financial constraints. However, preliminary studies with fingerprints older than 2 or 3 days have revealed that fingerprint detail smudges out and luminescence intensity decreases. This aging problem does not occur with fingerprints on smooth surfaces or with fingerprints on the sticky side of adhesive tape. The methodology used is promising and deserves further study, although it has not progressed to the point where it can be used in routine casework, particularly with older latent fingerprints. Figures, photographs, and 18 references (Author abstract modified)