Preliminary Study on the Effect of Heated Surfaces Upon Bloodstain Pattern Analysis

Bloodstain pattern analysis (BPA) involves the interpretation of distinct blood patterns found at crime scenes following a violent act. In this paper, we explored for the first time the effects of surface temperatures upon blood impacting a horizontal surface (steel) with its implications in BPA explored. Specific surface temperatures were explored over the range 24-250 degrees C which relate to the four major boiling regimes of liquid media; natural convection, nucleate boiling, transition boiling, and film boiling, where a series of blood drops tests were performed at varying impact velocities. Blood was found to separate into its components at temperatures of 50 degrees C+, displayed as temperature induced blood rings, where a single secondary and a series of further inner rings are exhibited. This consequently led to the development of a new constant C-d(heated) expressing the decrease in spread factor (D-s/D-o) at the secondary ring.