Guidelines Bloodstain Pattern Analysis
The following guidelines have been adopted (where applicable) from the Code of Practice and Conduct for Bloodstain Pattern Analysis from the Forensic Science Regulator (FSR-C-102 issue 2).
Training should include the following:
- Recognise and describe the elements of their quality system.
- Understand accreditation as it relates to BPA, including validation processes and proficiency testing (PT).
- Health and safety issues associated with BPA.
- The history of BPA.
- Scientific principles as they relate to BPA.
- The scientific method and its application to BPA experimentation.
- The principles of physics and fluid mechanics as they relate to BPA.
- Bloodstain classification and terminology.
- Bloodstain pattern principles and their application to BPA.
- Blood composition and related human anatomy and physiology.
- Injury and wounding, and their relationship to bloodstain pattern formation.
- The effects of surface characteristics on the resulting bloodstain patterns.
- The effect of environmental factors on the formation and/or drying time of bloodstain patterns.
- The characteristics of blood dynamics, including drop formation, oscillation, droplet flight paths, accompanying drops and secondary spatter.
- The relationship between the physical appearance of bloodstain patterns (size, shape, distribution, and location) and the mechanism by which they were created.
- The potential impact of searching methods, chemical testing, and enhancement techniques on BPA and other evidence types.
- Methods of documenting bloodstain pattern analysis, for example, video, photography, sketching and note taking.
- Methods for the preservation, collection and representative sampling of bloodstain pattern analysis.
- The relationship between bloodstain pattern analysis and other types of evidence.
- Development of examination and search strategies.
- Mathematical methods in BPA.
- Methods for the measurement of individual bloodstains.
- Trigonometric methods for impact spatter origin determination.
- The application of BPA to the reconstruction of bloodletting events.
- The reporting of BPA findings, conclusions, and opinions by written and/or verbal methods including the limitations of BPA and the application of experiments and reconstruction where necessary.
- How to review case information in order to aid BPA, understanding the limitations of that information, such that some may be missing or incorrect.
- aa) Hypothesis testing and evaluation of hypotheses using reconstructive experiments (hypothesis testing should be unbiased and attempt to test both prosecution and any reasonable defence hypotheses, either known or unknown).
- bb) An awareness of cognitive effects that may influence case assessment, interpretation and opinions, and procedures available to minimise effect of contextual bias on interpretation and evaluation, for example, blind assessment.
- cc) Laboratory experimentation and various BPA case scenarios factoring in error rates, limitations / reliability.
Selection of Test Methods
Techniques and strategies for examining BPA allow the scientist to:
- Devise and develop the examination strategy taking into account other evidence types;
- Preserve bloodstain evidence, for example, the management of fragile or vulnerable bloodstain patterns;
- Accurately record any items that will not be available for future examination or be altered during testing;
- Complete records to enable a full independent review of the findings and to facilitate any future case review.
Methods that can be used for documenting blood patterns include:
- Image capture (for example, video, 3D imaging).
Methods to identify individual patterns include:
- Determining the basis for classification (OSAC Bloodstain Pattern Classification Process Map);
- The use of ASB recommended terminology;
- Determining the relationship between an individual bloodstain pattern with its causal mechanism;
- The recognition of physical, physiological, wetting and chemical altering effects;
- The determination of directionality;
- The interpretation of voids, shadowing and limiting angles;
- The determination of valid conclusions from bloodstain pattern boundaries;
- Calculating an area of origin of blood spatter by:
- string method;
- tangent method;
- directional analysis;
- Consideration of the limitations of attempting to determine the sequence, aging and drying times of bloodstains;
- Using BPA as a basis for sample selection for testing (for example, DNA profiling);
- Use of assistive technology, such as, microscopy, specialist lighting and scanning to examine and evaluate bloodstains;
- Securing wetted items to minimise alteration of bloodstain patterns; and
- Awareness of the difficulties commonly encountered in the examination of bloodstain patterns (for example, bloodstains on dark surfaces, small bloodstains) and the consideration for additional searching.
Enhancing or revealing bloodstaining requires:
- An awareness of the range of techniques available to use (for example, luminol, leuco crystal violet, amido black, leucomalachite green, acid yellow);
- An understanding of what other biological/chemical material other than blood is revealed; and
- consideration of any specialised conditions, such as substrate, temperature or lighting required and limitations or effect when sub optimal conditions exist.