An accurate and methodical technique for documenting bloodstain patterns is invaluable in crime scene analysis.
As the old adage goes, “a picture is worth a thousand words.” However, in the field of crime scene investigation this saying should be changed to “a properly taken picture is worth a thousand words.” Never is this more true than when documenting bloodstain patterns at a scene. Proper documentation of a crime scene, and bloodstains specifically, verifies the integrity of the scene and the evidence within it; provides quality presentations for subsequent courtroom testimony; and allows for outside analysis by other experts.1 The fundamental goal of documenting bloodstain patterns is to accurately depict the patterns as you found them. This is accomplished through note taking, sketching, and photography. Additionally, videotaping may be helpful depending on the scene, but it should never replace photography.
Let’s first address note taking. Your notes should contain a detailed description of the physical characteristics of the patterns including size, distribution, location, shape, and physical features.2 When taking notes, remember to use terms like “reddish-brown stain,” “visually consistent with blood,” “bloodlike,” or some other term until laboratory analysis confirms that it is blood. These physical description details become important when classifying patterns into categories and will help to supplement your photographs. There are several classification systems used in the field of bloodstain pattern analysis. One of the most practical was developed by Stuart H. James, Paul E. Kish, and T. Paulette Sutton. In this taxonomy, patterns are categorized based upon their physical appearance and the mechanism that created the pattern. This is a conservative and holistic approach that uses the three primary groups of Passive, Spatter, and Altered as well as several subcategories under each group.3
As with your notes, the sketch will complement the photographs and will provide a graphic representation of the overall layout of the scene, the relationships between the scene and the evidence, and the specific locations of the bloodstain patterns. Consider using an exploded diagram to depict any patterns on walls. Sketches can also be valuable when analyzing bloodstains on clothing and can be very useful when the time comes to testify in court.
The road mapping technique was developed by Toby L. Wolson of the Miami-Dade Police Department’s Crime Laboratory and it allows for complete photo documentation of bloodstain patterns.4 The procedure involves using overall, medium, and close-up photographs combined with labels and scales. Separate pattern groups are identified and labeled and then important stains within that group are further identified and labeled accordingly. The labels and scales serve as “road signs” in the photographs and ensure that viewers are never “lost.” Most importantly, using this technique will allow others to properly analyze the patterns from the photographs without ever being present at the scene.
Remember to take your photographs of the scene and evidence in situ before adding scales/labels or using any chemical processing. Keep your camera lens perpendicular to the plane of the bloodstain and use the most appropriate lighting techniques for the situation. This usually requires using the flash off of the camera and side-lighting the stain. Also, using a ring flash will help when taking the close-up shots of individual stains by providing even lighting over the entire stain surface.
To correctly perform the road mapping technique, the following equipment is necessary (these items can be purchased from many crime scene equipment suppliers):
- Yellow paper (disposable) photographic scales (vertical and horizontal, 8’ x 8’)
- Adhesive mapping symbols (e.g. A, B, C, etc.)
- Adhesive scales (50mm/2”)
- Glue or tape
1. Identify the patterns you want to document, and photograph those patterns as they are (Photo 1). Road mapping can be used for all types of patterns but it is an especially important technique for impact patterns that will be reconstructed to determine an area of origin.
2. Apply the yellow scales with tape or glue so that they surround the pattern both horizontally and vertically (Photo 2). Make sure you use reference points for the placement of these scales such as the ground for the vertical scale and a corner of a wall for the horizontal scale.
3. Label each separate pattern with an adhesive mapping symbol (e.g. A, B, C, etc.). Photo 3 illustrates that A denotes an impact pattern, B a transfer pattern, and C a cast-off pattern.
4. Pick out the important individual stains within each pattern and label each stain with an adhesive scale (e.g. A1, A2, A3, etc.). With an impact pattern, choose stains that show directionality, allow for an accurate determination of the area of convergence, and that are closer to that area of convergence. Smaller stains are better choices than larger stains and there is no specific number of stains required, but it is best to select about eight to twelve stains for a proper reconstruction. Also, use the metric side of the scale and if you are dealing with a vertical surface, consider using a Torpedo level to mark a level line under each stain. This will orient the ground in each photograph (Photo 4).
5. Finally, begin to take your overall (Photo 4), medium (Photo 5), and close-up photographs (Photo 6) of each pattern until you have fully documented the scene. This technique can also be used when analyzing bloodstains on clothing and all of the same principles apply (Photo 7). Remember to use caution when using road mapping because it is an intrusive technique and should only be performed after you have taken your initial photographs and collected samples from the appropriate stains.
In conclusion, the road mapping technique provides a simple and systematic method for properly documenting bloodstain patterns, allowing the investigator to graphically illustrate the relationships between the patterns, the individual stains, and landmarks within the scene. It can be accomplished quickly, using reasonably priced equipment. By using this method, you can ensure that anyone viewing the photographs, such as independent experts, peer reviewers, and jurors, are never confused and are able to make judgments appropriately.
- Bevel, Tom, and Ross Gardner. Bloodstain Pattern Analysis. Boca Raton: CRC Press, 2008, 297.
- James, Stuart, Paul Kish, and T. Paulette Sutton. Principles of Bloodstain Pattern Analysis. Boca Raton: CRC Press, 2005, 264-265.
- Ibid., 67-70.
- Wolson, Toby L. Bloodstain Pattern Analysis Workshop Manual. Miami: Metropolitan Police Institute, 1997.
Daniel R. Winterich is a Senior Special Agent with the Ohio Bureau of Criminal Identification and Investigation and is assigned to the Crime Scene Unit where he provides investigative assistance throughout the state. He holds a J.D. from Cleveland State University, a B.S. from John Carroll University, and a Certificate in Criminal Justice Education from the University of Virginia. He is a member of the International Association of Bloodstain Pattern Analysts, a graduate of the 236th Session of the FBI National Academy, and a part-time lecturer at John Carroll University. He can be reached at email@example.com.