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Bloodstain Pattern Analysis (BPA)

Bloodstain patterns at a crime scene can reveal important information. By studying the shape, size and distribution pattern, an analyst can provide expert opinion on the physical events that created the bloodstain patterns. The analysis can refute or confirm suspects, victims and witness statements.

The first responding officers are responsible for appropriately protecting bloodstain evidence at the scene. Bloodstain pattern analysts should only be requested to attend a scene after consultation with the Forensic Identification member. Early involvement of a specially trained bloodstain pattern analyst can save time and effort by determining, if a case is a serious assault or murder versus a natural cause or self-inflicted injury.

Information a bloodstain pattern analysis may provide to an investigator:

  • Location and description of individual stains and patterns
  • Mechanism that created the stains
  • Direction a blood droplet was traveling (by calculating angles of impact)
  • Area of origin (location of blow into blood source)
  • Type of object used in attack (edged, blunt, firearm, etc.)
  • Minimum number of blows
  • The presence of a subject at a scene - linking suspects, victims and objects
  • Location of the victim, perpetrator, and objects during events and their movements
  • The sequence of events