Chemical Imaging of Latent Fingerprint for Forensic Evidence

As submitted by the proposer: For over 100 years, fingerprinting has been a major tool for identification in the criminal justice system. Unfortunately, fingerprints are often smudged, distorted, or overlapped with another print, and sometimes may not have a match in the database. When a fingerprint is left at a crime scene, it is not a simple array of black and white imaging pixels, but a mixture of tens or hundreds of biochemicals resultant from sweat and gland secretions, as well as artificial chemicals with which the individual had previously come into contact. The chemical information of the fingerprints could provide a new avenue in individual identification, in addition to the fingerprint database search. It may reveal the details of criminal activities or additional information about the suspect such as gender, age, or medical conditions. Mass spectrometry imaging is the most promising technique for chemical fingerprinting due to its extremely high sensitivity, label-free detection, and unbiased molecular characterization. In spite of the progress made in the last ten years, mass spectrometry based chemical fingerprinting is still far from practical use because of a few major bottlenecks, including low sensitivity for small molecules, ambiguity of chemical identifications, lack of robust protocols compatible with traditional forensic investigations, and demonstration of unique applications. The proposed research is designed to overcome scientific stumbling blocks keeping chemical fingerprinting from practical applications in forensics. Multiple strategies are incorporated in systematic and holistic approaches. Nanoparticles will be used to dramatically enhance mass spectrometry signals, while simultaneously visualizing latent fingerprints from a crime scene. Confident chemical identification will be made using the multiplex mass spectrometry imaging technology developed by the project investigators that can obtain not only mass spectral but also fragment spectral information in a single data acquisition. Additionally, high-spatial resolution finger pore images could be obtained simultaneously. As another innovative approach, the age of fingerprints will be traced from one or two day old fingerprints to a few weeks old using the diffusion of fatty acids and triacylglycerols. Finally, initial effort for a more advanced application will be made by exploring the potential of chemical fingerprinting to distinguish between individuals based on fatty acid, triacylglycerol, or amino acid compositions. Note: This project contains a research and/or development component, as defined in applicable law. ca/ncf