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

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 donor’s 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.

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