bloodstain patterns

Forensic Bloodstain Pattern Analysis

Effects of Surface Texture

• Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results 

• Rough surfaces (concrete, wood) usually result in irregular shapes with serrated edges, possibly with satellite spatter. 

Directionality

• Defines the direction a droplet was moving at the time it struck a surface. Tail points in the direction of the travel

Bloodstain Pattern Analysis

• Spatter-  small circular and or elliptical shaped stains

• Non-spatter- everything else 

Impact spatter occurs when an object impacts a source of blood, plain view exception

• Related small stains with consistent directional angles

• Radiating from a central point 

• It's important not to quickly associate the patterns with the common events that cause them

  • It is okay to just describe a pattern as an unknown pattern 

Classifying Impact Spatter

• Size of stains varies with speed of blood at time of impact 

• Low Velocity Spatter

  • Drops with diameters of 4 mm or more normally produced…

• Medium Velocity

  • Drops with diameters from 1-4mm with an applied force of 5-25 ft/sec. Usually associated with blunt force trauma 

• High Velocity

  • Diameter of less than l mm from applied force 100 ft/sec or faster. Gunshot wounds or explosions 

Gunshot Spatter

• Fine forward spatter from an exit wound and back spatter from an entrance wound 

Cast-off Spatter

• Created when a blood-covered object flings blood in an arc onto a nearby surface 

• Results of an object which is in motion or suddenly stops

Spurt pattern

• Large elliptical stains

• Line of stains or overlapping stains 

Arterial Spray Spatter

• Caused by an injury to the heart or a main artery and the pressure of the continuing pumping 

• Spiked pattern, similar to an EKG

Gush/Splash/Projected

• Large elliptical stains 

Expectorate Blood Patterns

• The presence of bubbles of oxygen in the drying drops or a lighter color as a result of dilution by saliva can differentiate a pattern created by expirated blood 

• Presence of an airway injury or blood in an airway (nose or mouth) 

Blood in Blood Pattern

• Surrounded by a random distribution of small spatter

• The spatter will generally not have consistent directional angles 

Satellite Patterns

• Get the notes!!!!!!

Contact/Transfer pattern

• Created when an object with blood on it touches one that does not have blood on it 

• The size and general shape of object may be seen in a simple transfer

• Result from the transfer of blood from one object to another without lateral motion

• Transfer demonstrates characteristics of an object 

Wipes and Swipes 

• Swipe- a pattern caused by a bloodstained object coming into contact through lateral motion with another object that is not bloodstained

  • Transfer stain in motion

• Wipe- a pattern caused by an object coming into contact through lateral motion with a pre-existing bloodstain on another object

  • Can be distinguished from swipes by the presence of skeletonization (ring around blood dro of the original bloodstain 

Flows

• The flow direction may show movements of objects or bodies while the flow is still in progress 

Blood Pools 

• Without any specific shape but conforming to 

Drop Trail Pattern

• A series of drops that are separate from other patterns, formed by blood dripping off an object or injury 

Void

• Created when an object blocks the depostion of the blood spatter onto a target surface or object and the spatter is deposited onto the object or person instead 

Use of Luminol detecting bloodstain patterns

• Spray on and shines blue, show blood when it can’t be seen like it was cleaned up

• Checking scenes of suspicious disappearances

Documenting Bloodstain Evidence

• Grid method and Perimeter ruler method