Forensic Serology: Blood Spatter 

Other Important Questions

 

Along with determining if the blood at a crime scene is human and where it originated in a three dimensional space, forensic serology must use other supporting evidence that blood spatter can provide to determine what kind of weapon was used, how many blows occured, the order events that occured at the scene, and if evidence supports or refutes witnessses stories.

 

By analyzing the cast-off paterns general classifications of weapons can be identified. In general, sharp objects produce narrower cast off patterns and minimal directional (forward and backward) spatter, while blunt weapons, like hammers, have a much wider cast off patterns .as a result of increased surface area, and a much larger impact on directional spatters.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cast off stains share similarities in their angles of impact due to each set of cast off sharing the same area of origin. As a result, sets of cast of stains can be analyzed and counted to determine a minimum number of swings after blood was drawn in a crime scene.For example in this diagram, a minimum of four swings occurred. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In order to determine the order of events, deductive reasoning is required while analyzing the plethora of patterns. For instance if there is a void pattern in the shape of a dresser on a whall that is otherwise covered in blood spatter, one can deduce that  something intercepted the blood from hitting the wall in that area, and it was moved prior to arriving at a scene. Likewise, wwipe and transfer patterns can help to place the order of events. If a seires of is wiped, they were distrubed after the initial attack, and an event can be noted to have occured after the initial assault. In the case of a transfer pattern, a shoe print captured in blood places an individual at a crime scene after the blood was drawn, which is crucial in determing the validity of a suspect's alibi.