This article reports on a research project that developed a method for the estimation of the time since deposition (TSD) of dried bloodstains, using UV-VIS spectrophotometric analysis of hemoglobin (Hb), that is based upon its characteristic oxidation chemistry.
The ability to determine the time since deposition of a bloodstain found at a crime scene could prove invaluable to law enforcement investigators, defining the time frame in which the individual depositing the evidence was present. Although various methods of accomplishing this have been proposed, none has gained widespread use due to poor time resolution and weak age correlation. In the current project, a detailed study of the Hb Soret band (max-412 nm) in aged bloodstains revealed a blue shift (shift to shorter wavelength) as the age of the stain increases. The extent of this shift permits, for the first time, a distinction to be made between bloodstains that were deposited minutes, hours, days and weeks prior to recovery and analysis. The extent of the blue shift was found to be a function of ambient relative humidity and temperature. The method is extremely sensitive, requiring as little as a 1 µl dried bloodstain for analysis. This project demonstrated the possibility of performing TSD measurements at the crime scene with a portable low-sample-volume spectrophotometer. 9 figures, 4 tables, and 34 references (publisher abstract modified)