Multi-Spectroscopic and Chemometrics Analysis for Forensic Determination of Blood Species

Blood trace is commonly found biological evidence at crime scenes. The main issues forensic investigators encounter upon retrieving blood samples is determining their origin. There is no statistical probability in the current examination methodology of potential blood evidence, and it is deemed subjective. Another method, involving DNA analysis, lengthy to perform and restricted due to its degradation and lack of samples. The main aim of this study was to evaluate the potential and suitability of tandem analysis using ATR-FTIR and UV/Vis spectroscopy as means for the characterization of blood samples in the context of forensic science. Conventional visual examination is insufficient to differentiate and classify spectra between blood from different animal species. Hence, to aid classification in each group, chemometrics analysis of the IR and UV/ Vis spectral dataset was employed using the combined techniques of principal component analysis and linear discriminant analysis (PCA-LDA). PCA-LDA results demonstrated that blood spectra of various animal species differed in the compositions of blood protein for example, amide A, I and II. The multivariate analysis based on PCA-LDA models indicated that ATR-FTIR and UV/Vis spectroscopy coupled with chemometrics provided excellent discrimination (94% correct classification) for the classification of blood samples from animal species. The non-destructive nature of vibrational and optical spectroscopic techniques and the success of chemometrics analysis demonstrated in this work have indeed offered a new dimension for the rapid identification of biomaterials of forensic relevance and essentially warrants further research. (author)