Advancing Forensic Analyses with Raman Spectroscopy

In recent years, there have been significant advances in the application of vibrational spectroscopy to the analysis of forensic samples. Igor K. Lednev, a professor in the Department of Chemistry at the University at Albany, the State University of New York, has been developing the use of Raman spectroscopy for a variety of forensic applications, including determining the age of blood stains and linking gunshot residues to specific ammunition–firearm combinations. He recently spoke to us about his work.

What have been the most important recent developments in vibrational spectroscopy, and Raman spectroscopy specifically, as they relate to forensic science (1)?

Vibrational spectroscopy techniques in general and Raman spectroscopy in particular have a lot to offer practical forensics because of their nondestructive nature and because they can be used for rapid, quantitative, confirmatory, and in-field analysis. As we described in our critical review article (1), the most recent developments include a universal, nondestructive, rapid method for detection and identification of biological stains based on Raman microspectroscopy and advanced statistics. At the University at Albany, we use multidimensional Raman spectroscopic signatures to differentiate and identify traces of body fluids (2,3). This novel methodology is expected to replace current in-field biochemical tests, which have several important limitations: They are mainly presumptive, they suffer from cross-reactivity, and a separate test is currently required for each body fluid type. In addition, our test allows for differentiating menstrual and peripheral blood, which can be instrumental for sexual assault cases, differentiating animal and human blood, determining the time since deposition of blood for up to two years, and providing information on phenotype profiling including the sex and race of the donor. All of this information is expected to be available immediately at a crime scene, helping the investigator determine what evidence to collect and to build a preliminary suspect profile based on the discovered body fluid traces. The van Leeuwen research group in Amsterdam, The Netherlands, used near-infrared (NIR) spectroscopy to develop a method to estimate the age of a bloodstain (4). Similarly impressive results have been obtained in gunshot residue research. The García-Ruiz research group (5) in Madrid, Spain, and our laboratory (6) reported independently on a new method to identify ammunition using Raman spectroscopy. An IR imaging procedure to automatically detect gunshot residue particles was also developed (7). Sergei Kazarian and coworkers from Imperial College London have made significant progress recently in using infrared spectroscopic imaging as a label-free method with a high chemical specificity and sensitivity for forensic applications (8). Edward Suzuki at the Washington State Patrol Crime Laboratory Division has used IR spectroscopy to identify pigments used in automotive paint (9). Jürgen Popp and coworkers in Jena, Germany, have used Raman spectroscopic techniques to detect pathogens, which is an extremely important concern for biosafety disciplines (10–12).

I would like to give a special emphasis to the impressive advances made recently in the area of spatially offset Raman spectroscopy (SORS). Pavel Matousek and coworkers from the Rutherford Appleton Laboratory pioneered the application of SORS as a novel noninvasive approach for a variety of forensic and biomedical applications (13,14). They founded Cobalt Light Systems in 2008 (recently acquired by Agilent Technologies) and have built a family of compact, fast, and relatively inexpensive instruments for airport security (testing sealed containers including bottles and cans) and the pharmaceutical industry. According to a recent press release, Cobalt's customers include more than 20 of the largest 25 global pharmaceutical companies and over 500 of their devices are deployed at airport checkpoints. I believe that this is the most significant practical application of Raman spectroscopy today with the highest potential impact on everyday life.

How did you come to be involved with forensic analysis?

I did not plan to. In 2003, our chemistry department launched a program in forensic chemistry, offering both bachelor's and master's degrees. We received a $1.5 M grant from New York state to build a new teaching laboratory, which was designed to mirror the crime laboratory at the New York state police department, located across the street from the university campus. As a member of the analytical chemistry faculty, I was charged with providing research opportunities for our new students. Mark Dale served as the director of the Northeast Regional Forensic Institute at the University at Albany at that time, and he kindly took me to the National Institute of Justice (NIJ) Conference in Arlington, Virginia. Listening to talks on the current methods in forensic science, I realized that there was huge gap between practical "modern" forensics and advanced analytical chemistry in general and spectroscopy in particular. On my return from Arlington, we immediately started working with Kelly Virkler, a PhD student at that time, on the application of Raman spectroscopy for the identification of body fluid traces. Kelly's first papers on this topic, published in Forensic Science International in 2008 and 2009, are among the most cited and downloaded articles from this top journal in the field (15,16).

Dr. Virkler now is a supervisor of the forensic toxicology lab at the NY State Police Forensic Investigation Center. We received our first grant from the NIJ in 2009.

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