The Use of Raman Spectroscopy for the Identification of Forensically Relevant Body Fluid Stains

Raman spectroscopy is fast becoming a popular technique in the forensic science discipline, and more recently its focus has turned to biological samples. This study reveals the ability of Raman spectroscopy to identify some forensically relevant body fluids, both individually and within mixed samples, that can be crucial in some forensic investigations. This study also further demonstrates the capabilities of Raman as a means for human blood identification in simulated crime scene samples to include bloodstains on a variety of fabrics, at varying dilutions, following laundering, and with the use of various blood-enhancement reagents. The impact of washing and blood-enhancement reagents reveals the importance of the choice of method and its bearing on subsequent Raman analysis

Analysis of Minerals Using Linearly Polarized Infrared Microspectroscopy

This is an extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Collecting Quality Infrared Spectra from Microscopic Samples of Suspicious Powders in a Sealed Cell

The infrared (IR) microspectroscopical analysis of samples within a sealed-cell containing barium fluoride is a critical need when identifying toxic agents or suspicious powders of unidentified composition. The dispersive nature of barium fluoride is well understood and experimental conditions can be easily adjusted during reflection–absorption measurements to account for differences in focus between the visible and IR regions of the spectrum. In most instances, the ability to collect a viable spectrum is possible when using the sealed cell regardless of whether visible or IR focus is optimized. However, when IR focus is optimized, it is possible to collect useful data from even smaller samples. This is important when a minimal sample is available for analysis or the desire to minimize risk of sample exposure is important. While the use of barium fluoride introduces dispersion effects that are unavoidable, it is possible to adjust instrument settings when collecting IR spectra in the reflection–absorption mode to compensate for dispersion and minimize impact on the quality of the sample spectrum

The Potential Interference of Body Products and Substrates to the Identification of Ignitable Liquid Residues on Worn Clothing

The question of whether deposits on clothing as well as their chemical composition are being mistaken for ignitable fluids is a concern for forensic analysts. Body products and oil secretions can have similar chemical profiles to ignitable liquid residues (ILRs) as a result of comparable chemical compounds that may be found in both sources. This study investigated whether substrates of unworn and worn clothing, with endogenous body secretions and body products could interfere with ILR analysis. Sample extraction was completed by passive headspace concentration with activated charcoal strips (ACS) and desorption with carbon disulfide followed by analysis with gas chromatography-mass spectrometry (GC–MS). Results showed that some body products produce similar patterns to heavy petroleum distillates and most clothing contained components that are commonly found in ignitable liquids. It was concluded that the clothing, body products and compounds released by the body all contribute to the GC–MS profile of worn clothing. These components can mimic or mask the presence of ILRs, however educated and experienced analysts would likely be able to differentiate these substrate patterns from ILRs

Is Forensic Science in Danger of Extinction?

Observations of modern day forensic science has prompted asking the question of whether this field is in danger of extinction. Although there have undoubtedly been meaningful advancements in analytical capabilities, we have overlooked several unintended practical and philosophical consequences. This article addresses three main areas of concern: the declining role of the generalist in an era of increased specialization, the role of education in preparing the next generation of forensic scientists, and the implementation of advanced instrumentation with a focus on statistical significance and field deployable instrumentation

Morphologically-directed Raman Spectroscopy for Forensic Soil Analysis

Morphologically-directed Raman spectroscopy (MDRS) is a novel yet reliable analytical technique that can be used for a variety of forensic applications, enabling scientists to gain more information from samples than they obtain using more traditional methods. In soil forensics, MDRS delivers particle size distribution and microscopic morphological characteristics for the particles present, and at the same time allows secure mineral identification. In this article, we explore the benefits of utilizing soil in forensic investigations, and demonstrate the value of applying MDRS. Two case studies illustrate the real-life potential and applications of this technology

Morphologically Directed Raman Spectroscopic Analysis of Forensic Samples

Morphologically directed Raman spectroscopy (MDRS) is a novel and reliable tool that would enable criminalists to obtain more discriminatory information from forensic samples than their current capabilities. MDRS combines automated particle imaging and Raman spectroscopy into one instrument. Particle imaging is performed to determine particle size and shape distributions of components in a blended sample. Particle size is an important physical property of particulate samples and can be used in conjunction with Raman spectroscopy in the analysis of a range of samples of forensic interest, including illicit and counterfeit drugs, soils, gunshot residue (GSR), and white powders. Although measurement of particle size distributions is routinely carried out across a wide range of industries and is often a critical parameter in the manufacture and analysis of many products and substances, it is not widely used in the forensic sciences. Raman spectroscopy is used in forensic science to determine the molecular chemistry of materials because it is rapid, reliable, allows for analysis without contacting the sample, is nondestructive, and enables detection at low concentrations. Combining these two analytical techniques into a single platform allows the individual components present within a blend or mixture to be independently characterized and compared

Rapid, Reliable and Reviewable Mineral Identification with Infrared Microprobe Analysis

Infrared microprobe analysis (IRMA) is a valuable technology for mineral identification. Prior to the discovery of X-ray diffraction, the polarised light microscope was the principal tool for identifying minerals. While X-ray diffraction and electron beam microanalysis made major contributions to mineralogy, IRMA contributes unique information about the chemistry of complex minerals. Using diamond internal reflection to collect infrared (IR) spectra of minerals is an approach that extends optical mineralogy to new levels. It is simple, direct and rapid. Traditional whole grain mounts or petrographic sections, used for polarized light microscopy, are analysed by IR internal reflection. Attenuated total reflection (ATR) spectra are collected by touching the diamond internal reflection element to areas of interest. Silicates, carbonates, nitrates, phosphates, hydrates and other minerals provide unique spectra for identification. Using the diamond ATR microscope objective allows for the selective isolation of individual minerals for simultaneous collection of microscopic, optical and IR data, thus enabling the indisputable identification of most minerals. Applying IRMA to forensic soil analysis is an example of using this IR spectral method. A library of diamond ATR spectra of common soil minerals was prepared. These reference data let the analyst confirm the identity of mineral grains in soil evidence. Polarised light microscopical examination is the primary step. Each phase is then characterized by its ATR spectrum and searched through the spectral library. IRMA unites light microscopy with IR spectroscopy to create a powerful system capable of identifying mineral grains and correlating microstructure with chemistry. This technique has great utility in the analysis of material in a forensic context, particularly in relation to trace evidence