Home -> Step by step guides -> Forensic blood spatter analysis
Equipment, Software, and Other Resources Required:
- Personal Protective Equipment: This includes disposable gloves, face masks, and goggles to prevent the contamination of evidence and personal exposure.
- Crime Scene Barrier Tape: To secure the scene and prevent unauthorized access.
- Measurement Tools: Including laser rangefinders, tape measures, and protractors for measuring the characteristics of blood spatter patterns.
- High-Resolution Camera: To document the scene and bloodstains.
- Blood pattern analysis software: This can be a professional software like HemoSpat which helps in recreating the crime scene and the events leading to the blood spatter.
- Crime Scene Lights: To identify blood traces which are not visible to naked eyes.
- Swabs and Sterile Containers: For collecting blood samples for DNA analysis.
- String for Stringing Method: Can be used to find the area of origin of the blood spatter.
Concepts related to Blood Spatter Analysis:
- Angle of Impact: The angle at which blood droplet strikes a surface which influences the shape of the bloodstain.
- Area of Origin: The three-dimensional location from which the blood spatter originated.
- Directionality: The direction in which blood was traveling when it impacted a surface.
- Velocity: The speed of blood at the time of impact, which influences the size of the droplets. High-velocity impacts (such as gunshot wounds) produce smaller droplets than low-velocity impacts.
Step-by-Step Guide for Forensic Blood Spatter Analysis:
Step 1: Ensure Safety and Secure the Scene
Upon arriving at the crime scene, ensure everyone’s safety and secure the perimeter using barrier tape. Wear Personal Protective Equipment to avoid contaminating the crime scene.
Step 2: Initial Examination
Take a thorough initial look at the scene without touching anything. This helps to get an understanding of the situation. It’s essential to prevent any changes to the original scene.
Step 3: Document the Crime Scene
Use the high-resolution camera to take pictures of the entire crime scene and the bloodstain patterns from different angles. Note down the conditions of the scene, including the temperature, the type of surface where the bloodstains are found, etc.
Step 4: Collect Blood Samples
Carefully collect blood samples with a swab, being careful not to disrupt the spatter pattern. Store the samples in sterile containers for further lab analysis.
Step 5: Measure Blood Spatter
Measure the size, shape, and distribution of blood droplet stains. It’s important to accurately measure the length and width of the stains to determine their angle of impact using trigonometry.
Step 6: Measure Angle of Impact
Using the measurements obtained, measure the angle of impact. This can reveal the direction from which the blood arrived.
Step 7: Use the Stringing Method
Attach strings to the blood drops and follow the directionality to identify the area of origin of the blood spatter.
Step 8: Use Blood Pattern Analysis Software
Input the collected data – the dimensions and angles of bloodstains, into the blood pattern analysis software. The software will assist to recreate the events led to the blood spatter.
Step 9: Interpret Bloodstain Patterns
Through the software and calculations, study the patterns to get clues about the event that caused the spatter such as the type of weapon, the number of blows, the position, movement of victim and perpetrator, etc.
Step 10: Compile the Findings
Document and compile all the findings, impressions, and interpretations into a comprehensive report for use in the investigation or courtroom.