How does one distinguish one type of weapon from another through the examination of bloodstains?

Bloodstains and splatter marks can leave numerous clues about attacks and injuries sustained. Bloodstains can relate information about the type of weapon used, where a person was hit, how many times they were hit, the order in which hits occurred, the movements of the victim, direction of attack, and more.

Many clues can reveal the type of weapon. If a bloodstain is long and straight and the droplets are elongated, you can infer the blood was moving fast. This might imply the use of a slash with a knife; blood flowing off the tip of a knife splashes out like paint from a brush. If the stain shows a big, circular spatter, you might think a high powered firearm was used; when a bullet creates an exit wound, it will pull a large amount of blood and tissue with it. Smaller projectiles will not evoke as much splash, so the power of the weapon can also be inferred. If the bloodstain shows a big, curved spatter of blood, there is evidence of a struck artery. Splashed blood on clothing can also give away a weapon. Blood on the dominant hand's sleeve would suggest the use of a melee weapon like a knife.

Bloodstains with large, round drops are from slow-moving blood and can be caused by slow bleeding as a result of lacerations or crushing blows.