Decoupling the Isotopic Source Code of Complex Mixtures: A Topological Trajectory Strategy for Dynamic Forensic...

Area of Science:

• Forensic Science
• Analytical Chemistry
• Geochemistry

Background:

• Tracing gasoline accelerants in arson investigations is challenging due to complex mixtures of geological signatures, refining artifacts, and environmental degradation.
• Traditional static fingerprinting methods struggle to differentiate these confounding factors in dynamic samples.

Purpose of the Study:

• To develop a novel chemometric framework for accurately tracing gasoline accelerants in forensic investigations.
• To overcome the limitations of existing methods in disentangling geological and process-induced variations in accelerant samples.

Main Methods:

• Implementation of a hierarchical chemometric framework integrating Nested Variance Component Analysis (VCA) and Multivariate Discriminant Trajectory Analysis (MDTA).
• Orthogonal decomposition of mixed isotopic variances to identify regional anchors and process-recording markers.
• Kinetic stress-testing to determine "Forensic Validity Windows" for weathering and combustion sampling.

Main Results:

• Isolation of a robust panel of three "Rayleigh-resistant" regional anchors and one process-recording marker.
• Quantification of "Forensic Validity Windows": regional signatures persist >48h weathering, process details require <2 min sampling during combustion.
• Discovery of a "Topological Memory Effect" where accelerant source trajectories maintain separation despite isotopic drift.

Conclusions:

• The proposed framework offers a generalized mathematical strategy for dynamic source tracking of accelerants.
• An open-source computational workflow ensures transparency and reproducibility for forensic analysts.
• This approach enables practical distinction of accelerant sources in arson and wildfire cases without extensive retraining.