Bloodstain Pattern Analysis Lecture Notes

Introduction to Bloodstain Pattern Analysis (BPA)

• BPA involves examining bloodstain patterns to recreate actions causing bloodshed.
• Utilizes principles of biology, physics, and mathematics.
• Key Questions Answered:
  • Origin of blood
  • Cause and direction of wounds
  • Victim and perpetrator positioning
  • Support for witness statements

Principles of BPA

• Blood is composed of plasma, serum, and solid components.
• Blood transitions from liquid to gel-like clot after leaving the body.
• Blood can leave the body as flow, drip, spray, spurt, gush, or ooze.

Types of Bloodstains

1. Passive Stains
   • Result from gravity; include drops, flows, and pools.
2. Transfer Stains
   • Occur when an object comes into contact with a bloodstain.
3. Projected or Impact Stains
   • Include spatter, gushes, splashes, and arterial spurts.

Blood Spatter Types

• Impact Spatter: Force applied to blood source.
• Projection Spatter: From arterial spurting or expirated spray.
• Gunshot Spatter: Forward and back spatter from gunshot wounds.
• Cast-off Patterns: Blood flung from a swinging object.
• Arterial Spray: Blood from a severed artery forms an arc pattern.
• Expirated Spatter: Blood mixed with air expelled from lungs.

Bloodshed Events

• Bloodstain evidence varies based on the crime's nature.
• Sharp force injuries produce smaller stains; blunt force injuries yield varied drop sizes.
• Gunshot injuries create mist-like spatter.

Interpreting Patterns

• Impact, velocity, surface, and angle affect stain shape.
• Angles can be calculated to deduce actions at the scene.
• Voids indicate objects or people blocking blood path.

Why and When Is BPA Used?

• Helps address questions like what, where, when, who, and what didn’t occur during a crime.
• Supports or corroborates witness statements and forensic findings.

Bloodstain Patterns That May Be Found

• Ranges from large blood pools to microscopic stains.
• Surface tension of blood affects stain formation.
• DNA profiling can determine individual blood sources in a pattern.

Collection and Documentation of Bloodstain Evidence

• High-resolution photography is critical.
• Blood samples are collected for DNA profiling using swabs or by removing stained objects.
• Analysts require formal training and ongoing education.

Analysis Process

• Pattern Analysis: Evaluates characteristics like size, shape, and location.
• Reconstruction: Uses pattern data to make contextual interpretations.

Determining Area of Convergence and Origin

• Use strings, mathematical equations, or computer software.
• Determines the victim’s position during bloodshed.

Expert Witness and Legal Standards

• Frye Standard: General acceptance in scientific community.
• Federal Rules of Evidence, Rule 702: More flexible, focuses on reliability and application.
• Daubert Standard: Judges as gatekeepers, considers broad scientific criteria.

Conclusion

• BPA cannot recreate entire events, only specifics.
• Results support findings from other forensic disciplines.
• Quality assurance includes training, peer review, and accreditation.

Additional Resources

• SWGSTAIN and IABPA provide resources and guidelines.
• Key references include works by Tom Bevel, Stuart H. James, and Richard Saferstein.