Upon blood exiting the body, hemoglobin in blood transits from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO) to methemoglobin (met-Hb) and ending up in hemichrome (HC). For forensic purposes, the fractions of HbO, met-Hb and HC in a bloodstain can be used for age determination of bloodstains when measured with Reflectance Spectroscopy [http://plosone.org/article/info:doi/10.1371/journal.pone.0021845].