What is Bloodstain Pattern Analysis?
Bloodstain Pattern Analysis (BPA) is the study of the size, shape, volume, directionality and distribution of bloodstains found at crime scenes and the mechanism's which may have caused them. BPA is one of several tools that can be used to help investigators reconstruct a crime scene. A lot of times the question is "Who done it?" Of course this is the ultimate question all investigators want to know; however, BPA concerns itself with questions in regards to how it was done and the sequence of events involved in the crime. My instructor teaches his students to use a "Holistic" approach to crime scene analysis. Holistic meaning to incorporate and consider all evidence when analyzing a crime scene. Some of the evidence I'm referring to would consist of: Crime Scene Photos/Sketches, Witness statements, Autopsy Reports and Police/Investigator Reports. A lot of times the analyst may not be able to view the crime scene and will have to rely on these items. Some of the things that bloodstains can tell us are:
Direction of travel/movements of victim or assailant and whether they were running or walking
Areas of convergence and area of origin of bloodstains
Minimum number of strikes/blows inflicted
Impact angle of bloodstains
May be used to confirm or refute statements of witnesses or suspects
Can indicate a passage of time; i.e., Blood clotting, Serum separation, Drying times
May indicate whether the victim was lying down, kneeling, sitting or standing when struck
May also give an indication of the device and/or mechanism used to cause injury
Bloodstains can provide insight on the sequence of events which transpired
- Can give an indication if any objects have been moved within the crime scene (voids)
Bloodstains can reveal to the investigator a lot about what happened at a crime scene and the sequence of events which transpired. Using BPA along with other available tools, investigators can ensure that a thorough investigation has been completed. To not consider bloodstain evidence at a crime scene where blood is present would be an error.