Blood is one of the most common and important types of physical evidence present at a crime scene. When liquid blood is acted upon by external physical forces, that blood is often distributed through the air in the form of droplets, with bloodstains and bloodstain patterns deposited on adjacent surfaces. Using the mathematical relationship that exists between the blood droplet and resultant bloodstain’s length and width ratio, the angle at which the blood droplet impacted the receiving surface can be determined. Using this relationship, it becomes possible for Bloodstain Pattern Analysts to determine the three dimensional Region of Origin for the blood source from which the bloodstains under examination have originated. A Bloodstain Pattern Analyst performs angle of impact calculations from bloodstains for the purpose of making a three dimensional determination of blood source Region of Origin. The reliability of that determination is based on an assumption that one of the most important biological properties of blood; the amount of red blood cells or hematocrit value, has no influence over the length to width ratio of a bloodstain. As a consequence the Impact angle = arcsine [width/length] calculation has been assumed accurate regardless of the 'unknown' hematrocrit value. This thesis investigated the effect of the hematocrit value on the angle of impact calculation and thus the ability to determine the three dimensional blood source Region of Origin. Bloodstains were created by releasing a series of 18µL droplets, with ten different hematocrit values, onto a ceramic tile at four different angles. The resultant bloodstain length and width was measured and impact angle calculated. Evaluation of the research data shows that the hematocrit value significantly affects the bloodstains length and width. However, it is apparent that there is close agreement between the known and calculated impact angles irrespective of the hematocrit value.

Bloodstain Pattern Analysis is a rapidly growing area of research in the forensic science field. It is not uncommon for blood to be present on surfaces such as clothing, furniture, carpet, and more, during the commission of a crime. . Research of how blood interacts with different porous surfaces, such as textiles and fabrics, is relatively unexplored in the field of forensic science. Prior to a bloodshed event in which blood may be deposited onto clothing, the fabric may have been laundered in a variety of ways. In this research, swatches of a 100% nylon, water resistant fabric were subjected to seventeen different laundering and soiling processes. The laundering products used included Tide® Liquid Laundry Detergent, Downy® Fabric Softener, Downy® Unstoppables In-Wash Scent Boosters, Bounce® Dryer Sheets, Clorox® Zero Splash Bleach Packs, and OxiClean™ Max Force Laundry Stain Remover. Soiling included wearing swatches of fabric and leaving them in direct sunlight. Whole human blood was inverted, vortexed, then transferred using a disposable transfer pipette. The sample was held 36 in./3 ft. above each sample at a 90-degree angle, using an apparatus made from a flat edge and a protractor to ensure consistency. Blood drops were deposited onto each swatch of fabric, photographed, and microscopically examined. The drip stains were measured and characteristics of the blood, fabric, and the interaction of the two were recorded. Results showed some trends, such as an increased breakdown of fabric structure when bleach was used, and an increase in wicking when treated with scent boosters. Overall, the results were varied in all comparisons.

Blood is a biological fluid frequently encountered at crime scenes and can be an important source of information regarding the events that occurred and individuals involved. Blood evidence can be the subject of bloodstain pattern analysis (BPA) to ascertain the details of a blood shedding event as well as deoxyribonucleic acid (DNA) analysis to identify potential individuals that were present at the event. BPA becomes more complicated when bloodstains are found on clothing items due to the wide range of fabrics and their inherent properties, along with a range of factors, including but not limited to, treatments, effects of laundering, and wear. The interaction between fabrics and bloodstains has not been wholly explored in the forensic literature. Additionally, most forensic research on bloodstain and fabric interactions have been conducted on laundered, absorbent fabrics. Waterproof fabrics are designed to repel water and protect underlying surfaces from the effects of weather such as rain and snow, often having very different properties from other fabrics. In this research, the characteristics of bloodstains deposited on waterproof and absorbent fabrics were assessed, as well as the ability to chemically detect the presence of blood after physical alteration of the stains. Six unlaundered, waterproof fabrics with different waterproof coatings, fiber content, and other properties in addition to three different types of absorbent fabrics were cut into swatches and utilized for this study. Whole human blood was used to create a variety of bloodstain types that are often observed at a crime scene: drip stains at two different impact angles, spatter stains, and transfer stains. Ten replicates were completed for all nine fabrics and each bloodstain type, for a total of 360 bloodstains. The dried bloodstains were photographed with a handheld digital camera and a digital camera mounted on a stereo microscope to better visualize the interactions between the blood and fibers. The bloodstained fabric swatches were then physically manipulated to assess the persistence of the stains and the ability of a presumptive blood assay to detect the remaining traces. Four mechanisms of blood deposition created bloodstains with different characteristics. Differences were observed among the variety of waterproof fabrics as well as the different absorbent fabrics. Bloodstains on the waterproof fabrics appeared to rest on the surface with very little wicking into the fabric. The largest drip stain diameters were observed on the cotton t-shirt, implying that the cotton t-shirt had the greatest wicking ability. Pearling of the blood droplets was observed on the waterproof fabrics used in this experiment, but appeared to occur irrespective of the type of waterproof finish applied. The drip stains on the nylon fabrics appeared flatter and frequently caved in at the center, even though the waterproof finishes were the same as two of the polyester fabrics, which produced more spherical drip stains. The contrasting appearances of the drip stains on cotton jersey and the cotton t-shirt is likely due to the presence of 5% spandex in the cotton jersey fabric. Bloodstain characteristics thus appeared to be influenced by fiber content, fabric structure and thickness, and the presence of waterproofing surface treatments, as well as the blood deposition mechanism. The bloodstains on absorbent fabrics did not separate greatly from the fabric after alteration and appeared largely unchanged. The bloodstains were dislocated from the waterproof fabrics to varying extents, but all greater than the absorbent fabrics. Traces of the bloodstains were frequently observed under the stereo microscope when the pre-existing stains were not observed macroscopically, indicating that a microscopic examination may be a useful tool in the forensic laboratory. The altered drip stains at both impact angles were overwhelmingly detected by the presumptive Kastle-Meyer blood test, with only a single instance of a negative result. In contrast, test results were more evenly split among the spatter stains on waterproof fabrics and were less likely to produce positive test results. Positive test results were obtained for the majority of altered stains, including stains that were not visible to the naked eye, indicating that a presumptive blood test may be useful for detecting latent bloodstains on clothing items such as the ones analyzed in this research.

Violent crimes involving bloodshed may result in the formation of a number of blood drops that move through air and impact onto a surface producing a bloodstain pattern. Bloodstain Pattern Analysis (BPA), the analysis of the position, distribution, size and morphology of the stains within the pattern present at a crime scene, may provide information about the events that gave rise to the bloodshed. The location of blood origin, i.e. victim’s position at the moment of wounding and (or) wound location, determination is of major interest to BPA. This study investigated the dynamics of formation and flight of blood drops commonly found at a crime scene (so-called passive, cast-off, impact and gunshot drops) with the aim to facilitate blood origin determination. Features of blood drop formation at passive dripping with correlation to dripping surface characteristics were studied experimentally. A numerical scheme for accurate blood drop flight characteristics modelling, including oscillations, deformation and disintegration, was developed and validated against a number of analytical and experimental cases with special attention to the passive blood drop oscillations and ultimate deformation at terminal velocity, cast-off and impact blood drop deformation and breakup features. This provided an efficient and accurate method for typical blood drop flight reconstruction from the blood origin to impact as well as from the bloodstain location to the possible blood origin. Factors affecting blood drop trajectory and blood origin estimation were studied using the developed scheme.

This thesis is divided into two parts, each of which examines aspects of bloodstain analysis where gravity is the main force applied to blood. Part I is a preliminary study on the dynamics of blood flow on various inclined surfaces and examines the use of blood analogs for easy test replication. The flow of uncoagulated human blood at different volumes and temperatures was examined on wood at a set angle of 1.5°, and on glass at varying incline angles. Glycerol solutions of 59% and 42% were used to represent blood at 23°C and 37°C respectively. Glycerol flow trials of similar volumes were conducted on wood, PVC and glass. Fluid flow plots of distance versus time exhibited double exponential curve behaviour, although a power-law relationship derived by H. E. Huppert's (1982) flow expression was obtained for blood flowing on inclined wood. Blood flow exhibited several observable characteristics; a decreasing width of the leading edge over time, and streaking and component separation of the leading region at very low speeds. On a glass surface, the width of the initial flow region decreased and initial speed increased with increasing angles. The glycerol analogs used in this study did not represent their blood counterparts well due to differences in physical properties of the fluids. Part II of this study focuses on the forensic value of passive bloodstains on three fabrics; 100% cotton drill, 65/35 polyester cotton, and 100% Shantung silk. 26 µL drops of 37°C human blood were deposited onto the three fabrics and paper from a height of 14 cm at various impact angles. The stains were photographed and analysed qualitatively and quantitatively using computational methods. 100% cotton drill, 65/35 polyester cotton and ironed 100% Shantung silk provided useful forensic values such as direction of travel and angle of impact. Overall, this study has provided useful preliminary data for further research work.

The causes of errors in the angle of impact calculation were investigated including the surface type, falling velocity and the method used to fit an ellipse to a bloodstain. As had been cited previously the angle of impact was generally underestimated, especially at acute angles and the reason for this was determined to be due to an overestimation of the length of a bloodstain. The surface type was found to significantly affect the accuracy of an angle of impact calculation and as the falling velocity increased, the angle of impact calculation became more accurate. High-speed photography was used to further investigate the formation of bloodstains on surfaces. It was found that the formation of the bloodstain varied depending on the surface type and the angle of the surface. Bloodstain pattern analysis involves the application of scientific techniques to reconstruct events that resulted in a bloodstain pattern. The position of the blood source in three-dimensional space is a fundamental element of this application. Currently little is known about the methods used by bloodstain pattern analysts to select bloodstains when determining the region of origin. Fourteen analysts worldwide were surveyed in order to ascertain this information. It was found that the methods used were variable and were often not based on scientific research. Research was therefore undertaken into bloodstain selection and in particular, which bloodstains should be selected for a region of origin analysis. As a result of these experiments, two sets of selection criteria were established, one for use when the region of origin is being calculated manually and one for when directional analysis is being used.

The causes of errors in the angle of impact calculation were investigated including the surface type, falling velocity and the method used to fit an ellipse to a bloodstain. As had been cited previously the angle of impact was generally underestimated, especially at acute angles and the reason for this was determined to be due to an overestimation of the length of a bloodstain. The surface type was found to significantly affect the accuracy of an angle of impact calculation and as the falling velocity increased, the angle of impact calculation became more accurate. High-speed photography was used to further investigate the formation of bloodstains on surfaces. It was found that the formation of the bloodstain varied depending on the surface type and the angle of the surface. Bloodstain pattern analysis involves the application of scientific techniques to reconstruct events that resulted in a bloodstain pattern. The position of the blood source in three-dimensional space is a fundamental element of this application. Currently little is known about the methods used by bloodstain pattern analysts to select bloodstains when determining the region of origin. Fourteen analysts worldwide were surveyed in order to ascertain this information. It was found that the methods used were variable and were often not based on scientific research. Research was therefore undertaken into bloodstain selection and in particular, which bloodstains should be selected for a region of origin analysis. As a result of these experiments, two sets of selection criteria were established, one for use when the region of origin is being calculated manually and one for when directional analysis is being used.

The success or failure of any criminal investigation often depends on the recognition of physical evidence left at a crime scene and the proper analysis of that evidence. Crime scenes that involve bloodshed often contain a wealth of information in the form of blood patterns, the location, and its cause. Any criminal investigation has specific tasks, from the time when the crime is reported to the reconstruction of crime scenes. A lot of work needs to be done. Once the investigation starts at the crime scene, BPA needs to be done at the crime scene and the investigating officer must identify this evidential tool. The investigating officer should not necessarily have specialised training in blood pattern analysis, but rather know when to use these experts at their bloody crime scenes. With the interviews and docket analysis done, the researcher found that this was a problem as the investigating officers, either had no knowledge on the subject of BPA or very little knowledge on this research. The purpose of this study was to determine the use of BPA to CSR, and for the investigating officer to realise that it is not just a bloody crime scene, but also contains a wealth of evidence. The researcher had two research questions. Once the investigating officer follows the objectives of criminal investigation, they should be able to have a strong case against the perpetrators. How could BPA be used in the reconstructing of a crime scene? The researcher wanted to bring it to the investigating officers’ attention that it is not just a bloody crime scene, but rather that it contains a wealth of evidence, which can give them a perspective of the movement of both the victim and perpetrator during the commencement of the crime. Regardless of the lack of knowledge of BPA, it is proposed that investigating officers are to be informed, either through station lectures or by yearly refresher workshops and courses of the evidential tool of BPA. When the bloody crime scene is reconstructed with the use of BPA, an insight of what transpired at the crime scene will help them to finalise their cases. For recommendations, it is proposed that investigating officers are to be trained in more in depth courses in criminal investigation as well as crime scene reconstruction and evidence collection using FSL. / Criminology and Security Science / M.Tech. (Forensic Investigation)