Discrimination of human and animal blood traces via Raman spectroscopy.

The characterization of suspected blood stains is an important aspect of forensic science. In particular, determining the origin of a blood stain is a critical, yet overlooked, step in establishing its relevance to the crime. Currently, assays for determining human origin for blood are time consuming and destructive to the sample. The research presented here demonstrates that Raman spectroscopy can be effectively applied as a non-destructive technique for differentiating human blood from a wide survey of animal blood. A Partial Least Squares-Discriminant Analysis (PLS-DA) model was built from a training set of the near infrared Raman spectra from 11 species. Various performance measures, including a blind test and external validation, confirm the discriminatory performance of the chemometric model. The model demonstrated 100% accuracy in its differentiation between human and nonhuman blood. These findings further demonstrate a great potential of Raman spectroscopy to the field of serology, especially for species identification of a suspected blood stain.