Bloodstain Pattern Analysis (BPA) is the field of forensic science that consists of the study and analysis of bloodstains at a known or suspected crime scene with the purpose of drawing conclusions about the nature, timing and other details of the crime. It is used mostly to study homicide or other violent crimes in which blood is present and can help in crime scene reconstruction. Since the late 1950s, BPA experts have claimed to be able to use biology, physics (fluid dynamics), and mathematical calculations to reconstruct with accuracy events at a crime scene, and these claims have been accepted by the criminal justice system.