Where did the blood come from? Target 2-3

Target 2-3 Where did the blood come from? What happens when we bleed? What can we learn from bloodstains?

3 Types of Bloodstains Passive Stains Transfer Stains Impact Stains Drips, drops, and pools Caused by gravity Transfer Stains Hand/fingerprints, footprints, smears Caused when a bloody object touches another object Impact Stains Spatter, spurts, and cast-offs Caused when blood is sprayed through the air by a weapon or injury

Passive Stains

Passive Stains Occur when blood drips to the ground/floor Larger pools indicate that the blood dripped for a longer period of time Blood trails can indicate which way a bleeding person went

Passive Stains Occur when blood hits a wall and then drips We can calculate the trajectory (angle) that the blood hit the wall – this can tell us how/where an injury occurred

Transfer Stains

Transfer Stains Occur when a bloody object touches a non-bloody object Handprints, fingerprints, shoeprints Weapons left on tables, floors, etc. Bloody clothing or rags We can use transfer stains to connect a person to a crime scene based on their prints, shoes, etc.

Impact Stains

Impact Stains Gunshot Spatter Occurs when the impact of a gunshot sprays blood out of the body High velocity spray (looks like mist) Size and spread of spatter will depend on caliber of bullet and range of shot Located behind the shooter (blowback) or behind the victim (through-and-through)

Impact Stains Gunshot Spatter

Impact Stains Projection Spatter Occurs when blood is forced out of the body under pressure Arterial Spurts: blood gushes out of an artery with each pump of the heart; large splashes, medium velocity Expirated Spatter: blood is exhaled with air through the mouth or nose; fine spray, low velocity

Impact Stains Projection Spatter: Arterial Spurts

Impact Stains Projection Spatter: Expirated Spatter *fine mist, but still larger drops and smaller area than gunshot!

Impact Stains Cast-Off Spatter Occur when an object is swung in an arc, flinging blood off as it moves Usually the result of a weapon being drawn back for another attack We can use cast-off trails to determine how many times a victim was attacked, and in which direction Sharp force weapons (such as a knife) will leave small, narrow trails of cast-off spatter Blunt force weapons (such as a baseball bat or a rock) will leave larger drops and wider trails

Impact Stains Cast-Off Spatter: Sharp Force Weapon

Impact Stains Cast-Off Spatter: Blunt Force Weapon

Void Patterns Void Patterns are areas that are less bloody than their surroundings Occur when people or objects block blood drips or spatter Can indicate that bloody objects were removed from a crime scene Can indicate the presence of a witness

Void Patterns