The Effect of Humidity on Blood Serum Pattern Formation and Blood Transfer

Abstract

A detailed knowledge of the drying properties of blood is important for a more complete understanding of the forensic information that may exist at a crime location. Although the effect of relative humidity on the general properties of blood drying has been evaluated, relatively little information exists regarding the alterations of blood serum distribution that may occur during the drying process. Moreover, the influence of humidity on the ability of dried blood drops to transfer from skin to absorbent material has never been studied. The data in the current report show that blood serum pattern formation is distinctly altered by increased humidity in drying drops of blood. In addition, these data document that high humidity conditions were sufficient to remoisten dried blood drops such that they were able to transfer to the absorbent material, with the original bloodstain pattern maintained.