Denim contributed a large fluorescent background in the spectrum of the blood stain due to the presence of dye (Fig. 7A). The fluorescence was so strong that no Raman peaks from blood or the substrate were easily discernible, thus making spectral subtraction very difficult. To solve this problem, a baseline algorithm was applied to the neat substrate and blood stain spectra before subtraction (Fig. 7E). The Vancouver Raman Algorithm subtracts a fifth-order polynomial, which is a common solution for removing broad fluorescence contributions from a Raman spectrum