Forensic Application of Near-Infrared Spectroscopy: Aging of Bloodstains

The age of a bloodstain can be used to establish the time when a crime was committed. As blood ages, deoxyhemoglobin (HbO2) is converted into methemoglobin (MetHb), which is evident by the color change from red to brown. Human blood from vein and capillary vessels was used in this investigation. Samples were prepared by placing blood on substrates such as gauze and glass. Near-infrared (NIR) spectra of the samples were measured periodically at ambient conditions for one month. Changes in the spectra can..