Imaging and Separation of Overlapping Fingerprints Based on Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Overlapping fingerprints are frequently encountered at crime scenes, yet remain challenging to interpret due to the difficulty of resolving individual ridge patterns. This limitation significantly diminishes their forensic value in personal identification. Here, we present a method combining matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) with multivariate statistical analysis for spatially resolved chemical differentiation of overlapping fingerprints. Principal component analysis (PCA) revealed that samples from Contributor A and Contributor B were distinctly separated along the first principal component, demonstrating high intra-contributor consistency and clear inter- contributor discrimination. Further classification using an orthogonal partial least-squares discriminant analysis (OPLS-DA) model yielded strong performance metrics (R²X = 0.976, R²Y = 0.965, Q² = 0.943), enabling effective resolution of overlapping marks from different individuals. Notably, a discriminative compound at m/z 228.2566 was identified and localized to a single contributor. This study demonstrates that MALDI-MSI, in conjunction with chemometric modeling, provides a rapid, cost-efficient, and high-resolution strategy for the forensic analysis of complex fingerprint mixtures, and holds promise for operational integration into routine casework.