Identification and Analysis of Body Fluid Traces Using ATR FT-IR Spectroscopy

Biological evidence is extremely important to solving crimes. Most of the tests to determine whether a stain found at a crime scene is biological require chemical treatments that can destroy the sample. The proposed research seeks to develop a new method for nondestructive, inexpensive, rapid, and on-scene detection, identification and characterization of body fluid traces in a forensic context based on attenuated total reflection Fourier transform-infrared spectroscopy. "Note: This project contains a research and/or development component, as defined in applicable law," and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). nca/ncf

It is often the case that evidence collected at a crime scene must be subjected to multiple analysis methods in order for the full picture of what the evidence shows to emerge. In an ideal situation, there would be unlimited amounts of a given piece of evidence, and this would allow the performance of all possible types of analyses, the results of which would provide a detailed composite of aspects of the crime and its circumstances. However, it is usually the case that the amount of a given form of evidence is very limited. In such instances, not all testing methods that are desired can be performed, and difficult decisions must be made about the forms of analysis to which the sample should be subjected in order to acquire data that are most definitive. This common occurrence fuels the continued development of technologies that can provide multiple forms of definitive information within a single experiment. Such methodologies would also streamline the analysis process and reduce the number of forms of analysis that must be performed on a single sample. This in turn would reduce the amount of evidence required for analysis.

The work proposed here would develop such a technique. The system would be capable of rapidly providing small-molecule spatial distribution maps of analyzed forensic evidence with minimal to no sample pre-treatment steps. For example, it would permit the mapping of components such as illicit drugs, “legal” mind-altering plant materials, or explosive materials in an individual’s fingerprints, while maintaining the image of the print. Since the observed print contains both the image of the chemical material to which the criminal has been exposed, and the image of the compounds normally detected by conventional fingerprint development methods, it would provide a direct connection between an individual and other material related to the crime. The technique proposed here would detect alterations made to questioned documents by mapping the spatial distributions of molecules unique to different pen inks (for example). Furthermore, it would enable detection of both inorganics and organics in gunshot residues through performance of a single experiment.

The approach involves the integration of a direct analysis in real time (DART) ion source, a high-resolution time-of-flight mass spectrometer, and a laser ablation system which would be operated in open air and optimized for the rapid, routine and facile detection of the spatial distributions of small-molecules in a wide variety of forensic samples.

"Note: This project contains a research and/or development component, as defined in applicable law," and complies with Part 200 Uniform Requirements - 2 CFR 200.210(a)(14). NCA/NCF

Biological samples are of an extreme importance on a crime scene. They are the only one type of evidences that can provide information about a direct donor. Most of the presumptive tests, which could specify whether or not a stain is a biological trace, require chemical treatment and therefore are destructive to the sample. Thus, a method which is nondestructive to the stain is desired and could eliminate non-informative traces and allow to focus on most valuable pieces of evidence. Tests confirming blood human origin are also mostly destructive to the sample and require laboratory settings. The ultimate goal of the proposed research project is to develop a new method for nondestructive, inexpensive, rapid, and on-scene detection, identification and characterization of body fluid traces in a forensic context. An attenuated total reflection (ATR) Fourier transform-infrared (FT-IR) spectroscopy was already found to be easy-to-use, nondestructive to the sample, requiring no to minimum sample preparation, and highly selective as any vibrational spectroscopic methods. Moreover, portable instruments are commercially available to perform all analysis on-field. The (bio)chemical composition of different body fluids was found to vary between them, and moreover, the composition of blood was proven to have quantitative changes within the same components between different species and different human donors. This study will include development of spectroscopic library and statistical models for identification of dry traces of five main body fluids, development and validation of statistical models for differentiating human and animal blood, and development of spectroscopic library and statistical models for determining donors sex and race based on a dry bloodstain. All samples will be chosen with gender, race, and age diversity for all aims regarding the human donors. Different breeds with mixed gender will be used for study involving discrimination between human and animal blood samples. After spectra will be collected using FT-IR spectroscopy, they will be loaded into statistical software for preprocessing and modeling for discrimination purposes. To strengthen the reliability and validity of the analysis, validation tests will be performed using internal and external operations of predictions, with new and/or unknown body fluid samples. ca/ncf