Introduction
Blood behavior conforms to specific scientific principles and therefore, professionals trained to perform bloodstain pattern analysis can analyze the blood evidence in a crime scene and come up with conclusions as to how the blood shedding happened. The stains may appear to have a random distribution in a crime scene, but the analysts can study the spatter patterns, transfers, and other marks. From the physical evidence, the investigators recognize and interpret the patterns to determine how they were created. These marks are then categorized to recreate the sequence of events that occurred following the bloodshed. Blood stain pattern analysis, therefore, examines the shapes, location and how blood stains are distributed to interpret the physical events preceding the bloodshed. BPA uses principles of biology, physics and mathematics and it is useful in corroborating witness statements as well as implicating or excluding possible culprits from the investigation.
According to National Forensic Science Technology Center (2016), bloodstain evidence is collected by cutting away samples of stained surfaces or materials, photographs of the stains can also be taken as well as drying and packaging the blood-stained items. Methods of collecting and documenting bloodstain evidence include photography of high resolution. Sketching materials such as a scale or a ruler are also used to provide accurate measurements of the bloodstain size and photos are taken from every angle while taking the measurements. Further documentation is achieved through taking, photographs, videos and making sketches of the crime scene (Brodbeck, 2012). The analysis of bloodstain pattern is performed in two phases, namely, pattern analysis and reconstruction. While conducting pattern analysis, the investigators scrutinize the physical aspects of the blood patterns. These characteristics include the size, shape, location, distribution, overall appearance and surface texture of the stains. The analysts can interpret the pattern types present and the possible mechanisms that caused them.
Reconstruction is achieved when the analysis data is used to explain the context of the stain patterns. For instance, the type of crime that has occurred, whether the stain patterns came from the victim or another person and the point from which the victim was bleeding. To help reconstruct the events, analysts use the direction and angle of the spatter to establish the areas of convergence and origin (National Forensic Science Technology Center, 2016). Investigators find the area of convergence by using strings to make straight lines through the long axis of specific drops; this follows the angle of impact through a flat plane. By following the lines to where they intersect, the analyst can discover the position of the victim when the stains were created. In determining the area of origin, investigators use a similar method but include height calculations to create a 3-D estimate of the victim's position when the blood drops occurred (Brodbeck, 2012).
Bloodstain pattern analysis has proven to be a reliable method of solving violent crimes as it provides vital clues to the occurrence of events. It, however, relies on the experience and opinion of the investigator and therefore, there is need to train more people. Additionally, quality control and quality assurance ought to be performed to ensure accurate results; this can be achieved through putting in place policies and procedures that govern activities relating to forensic laboratories. Governments may also require crime laboratories to achieve accreditation to confirm that it meets quality standards. Proper training of analysts as well as testing their competence is also a sure way of achieving quality control.
Appendices
Surface Studies – Vertical Drips on Various Surfaces
Retrieved from www.mvla.net. (2016)
Blood stain pattern on a rough wooden board
Retrieved from National Forensic Science Technology Center (2016)
Bloodstain Shape vs. Angle of Impact
Retrieved from www.mvla.net. (2016)
(a). Ninety degrees
Retrieved from http://www.neiai.org/neiai/uploads/Kent%20Smotherman/files/Bloodstain%20Pattern%20Analysis.pdf
Retrieved from www.mvla.net. (2016)
Retrieved from http://www.neiai.org/neiai/uploads/Kent%20Smotherman/files/Bloodstain%20Pattern%20Analysis.pdf
Impact Patterns
a).
Retrieved from http://www.neiai.org/neiai/uploads/Kent%20Smotherman/files/Bloodstain%20Pattern%20Analysis.pdf
b).
Retrieved from http://www.neiai.org/neiai/uploads/Kent%20Smotherman/files/Bloodstain%20Pattern%20Analysis.pdf
Size difference from a free falling drips of blood
References
Brodbeck, S. (2012). Introduction to Bloodstain Pattern Analysis. SIAK Journal-Journal of Police Science and Practice, 2, 51-57. Available at http://www.bmi.gv.at/cms/bmi_siak/4/2/1/ie2012/files/brodbeck_ie_2012.pdf
National Forensic Science Technology Center (2016). A Simplified Guide to Bloodstain Pattern Analysis. Available at http://www.crime-scene-investigator.net/simplified-guide-to-bloodstain-pattern-analysis.html
www.mvla.net. (2016). Bloodstain and Spatter Lab. Available at http://www.mvla.net/teachers/Lisaca/Forensics/Lists/Forensics%20Calendar/Attachments/724/Blood%20Spatter%20Analysis%20Lab.doc.
