Small air bubbles in the drops of blood are typically found in this type of spatter. Expirated spatter tends to form a very fine mist due to the pressure exerted by the lungs moving air out of the body.
The blood is propelled out of the breached blood vessel by the pumping of the heart and often forms an arcing pattern consisting of large, individual stains, with a new pattern created for each time the heart pumps.Įxpirated spatter - is usually caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth or an injury to the airways or lungs. (Courtesy of Brian Dew, Ron Smith & Associates)Īrterial spray - refers to the spurt of blood released when a major artery is severed. Counting the arcs can also show the minimum number of blows delivered.Ĭast-off spatter patterns from a pipe and a pool cue. Analysts can tell the direction of the impacting object by the shape of the spatter (tails point in the direction of motion). This occurs when an assailant swings the bloodstained object back before inflicting another blow. (Courtesy of John Black, Ron Smith & Associates)Ĭast-off - results when an object swung in an arc flings blood onto nearby surfaces. Typically, forward spatter is a fine mist and back spatter is larger and fewer drops.īack spatter from a gunshot wound on a steering wheel. Gunshot spatter will vary depending on the caliber of the gun, where the victim is struck, whether the bullet exits the body, distance between the victim and the gun and location of the victim relative to walls, floors and objects. Gunshot spatter - includes both forward spatter from the exit wound and back spatter from the entrance wound. The characteristics of blood spatter depend on the speed at which the blood leaves the body and the type of force applied to the blood source. (Courtesy of John Black, Ron Smith & Associates)īlood spatter is categorized as impact spatter (created when a force is applied to a liquid blood source) or projection spatter (caused by arterial spurting, expirated spray or spatter cast off an object). (Courtesy of John Black, Ron Smith & Associates) Passive bloodstain on a wooden floorboard. Impact stains result from blood projecting through the air and are usually seen as spatter, but may also include gushes, splashes and arterial spurts. Transfer stains result from objects coming into contact with existing bloodstains and leaving wipes, swipes or pattern transfers behind such as a bloody shoe print or a smear from a body being dragged.
Passive stains include drops, flows and pools, and typically result from gravity acting on an injured body.
Types of Stainsīloodstains are classified into three basic types: passive stains, transfer stains and projected or impact stains. It can flow, drip, spray, spurt, gush or just ooze from wounds. The presence of blood clots in bloodstains can indicate that the attack was prolonged, or that the victim was bleeding for some time after the injury occurred.īlood can leave the body in many different ways, depending on the type of injury inflicted. Except for people with hemophilia, blood will begin to clot within a few minutes, forming a dark, shiny gel-like substance that grows more solid as time progresses. But as anyone who has had a cut or a scrape knows, it doesn’t remain a liquid for long. Blood is in a liquid state when inside the body, and when it exits the body, it does so as a liquid. Blood contains both liquid (plasma and serum) and solids (red blood cells, white blood cells, platelets and proteins). To understand how analysts interpret bloodstains, one must first understand the basic properties of blood. Principles of Bloodstain Pattern Analysis