Raman spectroscopy to determine the time since deposition of heated bloodstains

At the scene of violent crimes, bloodstain evidence is one of the most frequently found and valuable types of evidence. Determining the time since deposition (TSD) can allow for investigators to draw conclusions as to when a crime occurred. In this proof-of-concept study Raman spectroscopy paired with chemometrics were utilized for the prediction of TSD for bloodstains aged under an extreme thermal environment (55 °C) up to 48 h post deposition. This temperature was chosen to represent an internal condition of a vehicle left in direct sunlight. It was found that peripheral bloodstains degraded at a faster rate when exposed to an extreme thermal environment than when aged under ambient conditions. TSD quantitative predictions were accomplished through the creation of two classification models.