Bloodstain Pattern Analysis: Techniques and Applications in Crime Scene Investigation
Introduction
Examining bloodstain patterns, which encompass splatters, transfers, and gaps, provides experts with the means to deduce significant information from a crime scene. This type of evidence requires analysts to understand blood patterns and figure out how those patterns were made. In this context, bloodstain Pattern Analysis (BPA) entails the examination of bloodstains at a crime scene to decipher their occurrence and investigate the origin of blood deposition. Since the movement of blood adheres to particular scientific principles, its proper documentation allows for dedicating numerous clues, such as the impact angle, directionality, and area of its origin.
Procedures in Bloodstain Pattern Analysis
BPA analysts employ scientific techniques to investigate bloodstained evidence at a crime scene. This includes gathering information, observing, documenting, analyzing, evaluating, drawing conclusions, and reviewing the work by other experts. The correctness and reliability of the results can be ensured by allowing independent analysts to replicate all tests and experiments (ChoromaĹ„ski, 2020). The place where the analysis is conducted will depend on the case’s intricacy and the absence of a specialist in the local vicinity. Consultants from outside are often hired if no experts are available locally.
The process of BPA involves two primary stages: analyzing the patterns and reconstructing the scene. The pattern analysis field explores stains’ appearance, encompassing their dimensions, forms, locations, and textures (Moza et al., 2023). During this stage, analysts aim to comprehend the existing patterns and the reasons behind their occurrence. Afterward, the analysis data is utilized in the reconstruction stage to explain the patterns of stains (Moza et al., 2023). It is possible to obtain details regarding the nature of the crime, the blood’s origin, and factors that could impact the stain’s current state.
Impact Angle of Bloodstains
The movement of dropping blood determines the observable blood patterns or forms. The round shape of blood droplets coming out of a wound results from the surface tension in the liquid blood (Gkikoka & Amankwaa, 2023). When blood droplets come into contact with the surface, they exhibit a denser texture than water, adhering firmly and gradually drying out. Multiple elements can impact the size and shape of a bloodstain upon impact with a surface. In most cases, when one drop of blood falls and lands vertically, it forms a circular shape.
When the droplet descends from a higher position, the bloodstain’s dimensions progressively increase until it reaches a definitive point of constant descent speed, unable to enlarge further. The stain created by a droplet falling at its maximum speed remains unchanged in size (Chashechkin, 2019).
Thus, by examining the sizes of bloodstains, experts can determine whether a person’s bleeding was upright or close to the ground, aiding the reconstruction process. The appearance of a bloodstain can be altered depending on the surface it lands upon. Stains with smooth edges will form circular shapes on sturdy and sleek surfaces. However, stains on more delicate, porous surfaces will exhibit an uneven form with jagged or curved boundaries.
Altering the angle at which a blood droplet strikes a surface causes a modification in the shape of the resulting bloodstain. The bloodstain shape will appear elongated, resembling an ellipse or oval, when the impact angle is reduced or more acute(Wang et al., 2021). To determine the angle of impact, experts can utilize a viewing loop or a metric ruler equipped with a small scale with measurements in increments of half a millimeter or less. They add a small circular mark on top of the stain(s) to gauge the size and shape of each stain in a particular design (ISPLD, 2021).
By assessing the length and width of the stain, experts can determine the angle at which the blood dropped. However, it is important not to include additional or protruding stain sections during measurement. The length and width of a bloodstain can be assessed by employing trigonometry. In this context, ISPLD (2021) encloses the following formula: “Sin-1 (width Ă· length) = angle of impact” (p. 6). Subsequently, it can be employed with a scientific calculator to determine the impact angle.
Establishing Stain Directionality
The direction and origin of the bloodstain can be determined by analyzing its shape. The direction of the blood drop is typically indicated by the trailing end or residual wave of the bloodstain. In this context, the bloodstain pattern’s directionality refers to the movement of blood and the angle at which it strikes an object (Zou & Stern, 2022). Analyzing the pointing direction of the stains – stain directionalities – in the two-dimensional area allows experts to identify the origin of the spatter-producing event (Bettison et al., 2021). The mentioned area is commonly referred to as the area of convergence; along with the impact angle, they are instrumental in the reconstruction stage of the BPA.
Area of Origin and Point of Convergence
The area of origin is another crucial term in the second stage of BPA. It implies the space in three dimensions where BPA experts can employ spatter patterns to establish their point of origin (Mishra et al., 2022). Two steps need to be undertaken to identify the source of the blood following an impact.
Firstly, there is a selection process of particular bloodstains at the impact location. To determine their origin, one traces a line through the middle of each stain, extending it back to its starting point. All the lines will converge at a specific spot referred to as the point of convergence (Mishra et al., 2022). In the subsequent stage, the angle at which blood droplets strike the surface will be utilized to incorporate an additional dimension into the investigation.
Documenting Bloodstain Patterns
Employing high-quality cameras is the prevailing method for capturing images of bloodstains. Precise measurements are obtained by placing a ruler or scale alongside the bloodstain while capturing images from multiple angles (Triveni, 2020). Experts frequently collect stored items, ensuring no damage was caused to them. The scrupulousness of the process is crucial since unchanged patterns can provide enhanced understanding and additional evidence even through the sole utilization of videos and drawings depicting the scene and blood stains.
Conclusion
Overall, a thorough investigation and careful documentation of blood pattern evidence allows criminalists to deduce numerous details regarding the occurred crime. For instance, impact angle, pattern’s directionality, and area of origin point to the place of the bloodshed. Moreover, they yield clues to the bleeding body’s approximate position, allowing experts to reconstruct the crime. Documenting this evidence with high precision is crucial to obtain the highest quality results.
References
Bettison, A., Krosch, M. N., Chaseling, J., & Wright, K. (2021). Bloodstain pattern analysis: Does experience equate to expertise? Journal of Forensic Sciences, 66(3), 866-878. Web.
Chashechkin, Y. D. (2019). Evolution of the fine structure of the matter distribution of a free-falling droplet in mixing liquids. Izvestiya, Atmospheric and Oceanic Physics, 55(3), 285-294. Web.
Choromański, K. (2020). Performing bloodstain pattern analysis and other forensic activities on cases related to Coronavirus diseases (Covid-19). International Journal of Legal Studies (IJOLS), 7(1), 13-24. Web.
ISPLD. (2021). Bloodstain pattern analysis: Procedures manual. Indiana State Police Laboratory Division.
Gkikoka, E., & Amankwaa, A. O. (2023). Distinguishing between stamping in blood from walking through blood using blood pattern analysis. Forensic Science International, 350, 1-9. Web.
Mishra, A., Singh, J., Singh, C., & Dwivedi, A. (2022). Bloodstain pattern analysis. In A. Barbaro & A. Mishra (Eds.), Manual of Crime Scene Investigation, pp. 101-117. CRC Press.
Moza, B., Mukherjee, D., & Verma, P. (2023). Blood stain pattern analysis: A comprehensive review of methods, reliability of computerized analysis, and future advancements. Sciences, 1(1), 5-10. Web.
Triveni, K. (2020). Bloodstain patterns and the use of digital aid in interpretation: A review. International Journal of Engineering Applied Sciences and Technology, 5(4), 339-342.
Wang, F., Gallardo, V., Michielsen, S., & Fang, T. (2021). Fundamental study of porcine drip bloodstains on fabrics: Blood droplet impact and wicking dynamics. Forensic Science International, 318. Web.
Zou, T., & Stern, H. S. (2022). Towards a likelihood ratio approach for bloodstain pattern analysis. Forensic Science International, 341. Web.