This article reports on a project that used surface enhanced Raman scattering specificity for the detection and identification of dried bloodstains.
Surface enhanced Raman spectroscopy (SERS) provides highly specific vibrational signatures that identify dried blood for a variety of forensic applications. SERS spectra on Au nanoparticle substrates excited at 785 nm were found to identify dried stains of human and non-human blood from seven animals and distinguish stains due to menstrual and peripheral blood. In addition, the unique SERS bloodstain spectrum was distinct from the SERS spectra of 30 red-brown stains of potential household substances that could be visually mistaken for bloodstains and from food stains that have been shown to give positive results with presumptive colorimetric blood tests. Finally, a SERS swab procedure has been developed and demonstrates that the substrates that a blood sample dried on does not offer any Raman or fluorescence interference for the SERS identification of dried blood. Such bloodstains on porous and nonporous materials are all identical and exclusively due to the heme moiety of hemoglobin. Optimized selection of the extraction solvent is found to control the chemical composition of molecular components appearing in the SERS spectrum of complex, multicomponent biological mixtures, such as body fluids. (publisher abstract modified)