Forensic blood spatter

Blood Spatter Analysis : 

Blood Spatter Analysis CSI UMMC Some sections reprinted with permission of Dr. Ed Waldrip and the Southern Institute of Forensic Science

Blood Pattern Analysis : 

Blood Pattern Analysis The use of physics and math to interpret bloodstain patterns within a forensic setting May show: Activity at scene Number of blows Position of victim and assailant Whether death was immediate or delayed Weapon characteristics

History : 

History 1894 - Pitorowski wrote earliest reference to bloodstain pattern analysis 1939 - Balthazard was first to use physical interpretations of stains 1955 - Dr. Paul Kirkused bloodstain pattern interpretation as a defense witness in the Sam Shepherd case 1971 - Professor Herbert MacDonnell promoted bloodstain pattern interpretation as a tool for modern criminalistics 1983 – The International Association of Bloodstain Pattern Analysis was formed

Basic principles : 

Basic principles A free falling drop of blood forms a sphere or ball. A spherical drop will break When it strikes another object When acted upon by some force

Spatter size is dependent upon velocity : 

Spatter size is dependent upon velocity Low velocity spatter is about 5 ft / second and usually 3 mm or greater in diameter and indicates blood is dripping Medium velocity spatter is 5 – 25 ft / second with a <3 mm diameter and usually indicates blunt trauma or sharp trauma or it could be cast-off High velocity spatter is 100+ ft / second with a spatter of < 1 mm indicating gunshot trauma, power tools, an object striking with extreme velocity (airplane prop) or an explosion, may be referred to as fly specks

Determining Location of Blood Source : 

Determining Location of Blood Source Direction of travel – tail will point in direction of travel Angle of impact Vertical drops are circular Drop elongates as angle increases Measure width and length then calculate angle it struck the surface Attach string lines to each of the spatters and lines converge at the blood source

Angle of Impact“The tail tells the tale” : 

Angle of Impact“The tail tells the tale” 90 degrees – 60 degrees – 30 degrees – 10 degrees –

Slide 8: 

String Convergence in a 2 Dimensional Plane Convergence

Cast-off Bloodstains : 

Cast-off Bloodstains

Arterial Gushing : 

Arterial Gushing

Calculated point of origin : 

Calculated point of origin Closer for high velocity spatter or when stains originate closer to where the spatter occurred

Other Patterns in Blood : 

Other Patterns in Blood Transfer patterns (gun, knife, hand, foot…) Void patterns (indicating some object was removed or a person was hit by spatter) Flow patterns (may indicate movement with change in flow)

Drying Time : 

Drying Time Drying begins at periphery and proceeds inward Drying time is affected by Surface type Amount of blood Climatic conditions Skeletonization Partially dry stains leave a ring that outlines original spatter The drier the stain, the less skeletonization shown

Clotting Time : 

Clotting Time Clotting time outside the body ranges from 3 – 15 minutes Spattered clots indicate that time passed between the initial bleeding and later blows Coughing of clotted blood may indicate post-injury survival of victim

Group Activity : 

Group Activity Obtain the blood solution, dropper, protractor and paper plate Drop one drop of blood from 3 feet above the plate with the plate at 90 degrees to the dropper Drop ten more drops in different locations but with each subsequent drop decrease the angle between the dropper and the plate Record the angles used and observe the drops Describe what you see