Raman spectroscopic signature of blood and its potential application to forensic body fluid identification

Abstract

Near-infrared (NIR) Raman spectroscopy was used to measure spectra of dried human blood samples from multiple donors. Two major questions addressed in this paper involve the influence of sample heterogeneity and potential Raman spectral variations that could arise between different donors of blood. Advanced statistical analysis of spectra obtained from multiple spots on dry samples showed that dry blood is chemically heterogeneous, and its Raman spectra could be presented very well as a linear combination of a fluorescent background and two Raman spectroscopic components that are dominated by hemoglobin and fibrin, respectively. Each sample Raman spectrum contains the same major peaks, but the relative contribution of the hemoglobin and fibrin components varies with the donor. Therefore, no single spectrum could adequately represent an experimental Raman spectrum of dry blood in a quantitative way, but rather the combination of hemoglobin and fibrin spectral components could be considered to be a spectroscopic signature for blood. This proof-of-concept approach shows the potential for Raman spectroscopy to be used in forensic analysis to identify an unknown substance such as blood.

Discriminant Analysis of Raman Spectra for Body Fluid Identification for Forensic Purposes

“…Fluorescence and Raman spectroscopies are among the most promising nondestructive methods for confirmatory identification of body fluids [4][5][6][7][8][9][10][11][12]. The less sensitive Raman spectroscopy in comparison with fluorescence has higher selectivity and specificity to biochemical species and could potentially be useful in resolving mixtures of multiple body fluids with minimal sample preparation or manipulation [4][5][6][7][8][9][10][11]13].…”

“…Advanced statistical methods allow for retrieving of reliable information from data sets that is not otherwise evident. We have been successful in developing and applying advanced statistical analysis of Raman spectra for biochemical [19][20][21][22][23][24][25][26][27] and forensic purposes [7][8][9]11,13].…”

“…In addition, one can expect that the composition of body fluids varies from donor to donor. We have recently investigated the effect of dry body fluid heterogeneity and spectral variations due to multiple donors [7][8][9]. As a result, multi-dimensional Raman spectroscopic signatures have been developed for dry traces of blood, semen and saliva based on Principal Component Analysis (PCA) [7][8][9].…”

Body Fluids and Spectroscopic Techniques in Forensics: A Perfect Match?

“…In outline, the representative Raman spectra of blood, semen, vaginal fluid, saliva and sweat have been proposed as shown in Figure 3, information about their chemical composition has been obtained from the study of their spectral bands and several studies proving the differentiation of these five body fluids based on their characteristic Raman signatures by using chemometrics have been published [33][34][35][36][37][38]. Moreover, multivariate classification models have been developed in order to identify and classify unknown fluids, even in mixtures [39][40][41].…”

“…For example, a large part of the studies were carried out by analysing samples of body fluids on glass slides or directly placed onto the instrument [25,[33][34][35][36][37][38][39][40][41], which is an extremely unusual substrate in real cases. In addition, studies in which stains were prepared on different clothes such as cotton, polyester, acrylic or wool, exclusively correspond to blood [18][19][20][21][22][23]27,30,31] except for studies [24,26].…”