Bloodstain pattern analysis is the study of stationary bloodstains that assist in the reconstruction of specific spatial and sequential events that occurred prior to and during the act of bloodshed. It can determine the place from which the blood originated, the distance between the origin and spot where the blood was deposited, the type and direction of the impact that created the bloodstains, and the type of object that produced the bloodstains. Bloodstain pattern analysis can also provide information on the minimum number of blows that were administered; the position of the victim, assailant, and items during and after bloodshed; the movement and direction of the victim, assailant, and items after bloodshed; and the quality of statements given by the suspects or witnesses about the event. This article discusses the general dynamics of blood drops that yield bloodstains, the interpretation of spatter patterns, patterns of "cast-off" blood, the determination of weapon types from bloodstain patterns, and the establishing of the blood's impact angle. Also discussed are transferred bloodstains and the preservation of evidence.