Software for the trajectory analysis of blood-drops: A systematic review

3D scanning a crime scene to enhance juror understanding of Bloodstain Pattern Analysis evidence

There are numerous crime scene investigation applications of 3D scanning that have been previously documented. This paper documents the application of a 3D point cloud in the presentation of Bloodstain Pattern Analysis evidence to mock jurors. 150 mock jurors viewed a presentation of Bloodstain Pattern Analysis evidence from a murder trial in the UK. After viewing the evidence, the participants were tested on their knowledge of the evidence and repeated the test again 2 weeks later; to simulate criminal trial conditions; whereby there is a time lapse between the initial viewing of evidential material and deliberation. This paper found that the mock jurors who additionally viewed a 3D flythrough of a point cloud of the crime scene, better retained knowledge of the evidence over time, reported a greater ability to visualise the crime scene and had higher levels of interest in the evidence. Crucially, the 3D flythrough group did not report different levels of confidence in the accuracy of their memories of the evidence, nor different levels of emotional arousal to the group that viewed the evidence without the 3D presentation. Together, these findings suggest that 3D scanning of crime scenes, and the resultant point cloud's presentation to jurors, could add further value to the justice system when spatial information, such as Bloodstain Pattern Analysis evidence, is presented.

Assessing iPhone LiDAR & Recon-3D for determining area of origin in bloodstain pattern analysis

Bloodstain pattern analysis (BPA) has proven to be a useful tool in forensic and criminal investigations for quite some time. Traditionally, documenting a crime scene for a bloodletting event was completed using manual techniques, physical strings, and a tape measure. In more recent years, laser scanners and 3D software programs have become a preferred method to capture accurate data that improves the validity and reliability of BPA. The initial cost of laser scanning equipment is relatively high, rendering these systems inaccessible to some police and smaller agencies. Recon-3D is a newly developed iPhone application that utilizes the iPhone LiDAR sensor in combination with video data to create 3D point clouds of crime scenes. To assess the viability of Recon-3D for area of origin analysis, two tests were performed. One was a series of bloodstain impacts which were analyzed in FARO Zone 3D software, while the second was a series of 6 repeated Recon-3D scans of two 90-degree walls which was then compared to the FARO Focus S350 scanner using CloudCompare software. A total of eight impact patterns were made at three different distances from a wall. The area of origin was measured and compared to the known location of the blood source. The average total 3D error for the area of origin set at 25, 50, and 100 cm from two perpendicular walls was found to be 6.04, 15.16, and 36.59 cm, respectively. These results are similar to past studies where programs such as HemoSpat have been used. The results of the point cloud comparison show that on average, 95% of the points from Recon-3D fall below a threshold of 3.6 mm when compared to a FARO Focus S350 laser scanner. Thus, the results of this test suggest that Recon-3D is an accurate and affordable scanning application for bloodstain patterns at crime scenes and the data provide acceptable results for area of origin analysis in BPA programs which accept laser scanner data.

Empirical investigation of passive blood drop trajectory and first point of contact on inclined surfaces

The first point of contact between a spherical blood drop and a surface is related to the angle between the trajectory of the blood drop and the surface being struck. This angle is often referred to as the impact angle which can be estimated by knowing the width and length of the resultant elliptical bloodstain. Most software programs dedicated to area of origin analysis indicate the location of the backtracked bloodstain trajectory to be at the geometric centre or at the tip of the bloodstain ellipse. However, it is unknown how the first point of contact and the blood drop trajectory (here defined as the locus of the centre of mass of the drop as it travels) are related empirically. Thus, this study aims to look at how the initial point of contact and the trajectory at the impact of a blood drop relates to the formed bloodstain ellipse. Two volumes of blood (0.013 ml and 0.071 ml) were dropped from a height of 10 cm and 40 cm onto an inclined surface at 0°, 15°, 30°, 45°, 60°, and 75°. The transition from a spherical blood drop to an elliptically shaped bloodstain was recorded using a high-speed camera for all tests. A total of 72 ellipses were analyzed to determine the location of the first point of contact and trajectory point of the blood drop and how they relate to the formed elliptical bloodstain. A relationship was found between the first point of contact and the bloodstain trajectory which was dependent on the impact angle. However, there were clear deviations from theoretical assumptions due to blood drop oscillations, the effects of gravity, and the natural fluid characteristics of blood. The results of this study may assist bloodstain pattern analysts and software developers by more accurately applying the location of the blood drop trajectory based on empirical data.

Distinguishing between stamping in blood from walking through blood using blood pattern analysis

Bloodstains are typically encountered in violent incidents involving the use of a weapon or physical actions, such as punching, kicking, or stamping. Bloodstain pattern analysis can provide inceptive evidence or intelligence about what happened in an alleged incident, the sequence of events, along with indicating possible suspects if blood is analysed through DNA profiling. This research project focused on the differences in patterns created on footwear during a violent action, such as stamping on a person, and a non-violent action, such as walking through a pool of blood. In this project, several experiments were designed to simulate the stamping and walking actions on a surface wet with blood: carpet, lino flooring, and belly pork meat. Two volunteers with varying body weights were recruited to perform the two actions, using a pair of trainers and a pair of Wellington boots. Defibrinated horse blood was used to simulate real human blood. It was found that the patterns created from stamping and walking through blood differed by the type of pattern and the number and size of stains. The footwear used in the stamping action was characterised by a larger contact stain on the sole than those used in the walking actions: ∼209 mm in length by ∼92 mm in width versus ∼65 mm in length by ∼60 mm in width. The stamping action produced a large number of impact spatters (∼435) on the sides of the footwear versus no impact spatters in the walking actions. The presence of impact spatters was found to be the most prominent feature that differentiated between the two actions. The findings were statistically significant (p < 0.05) and could assist in evaluating whether a defendant was actively involved in a stamping action, or the evidence found was due to innocent reasons.

A Virtual, 3D Multimodal Approach to Victim and Crime Scene Reconstruction

In the last two decades, forensic pathology and crime scene investigations have seen a rapid increase in examination tools due to the implementation of several imaging techniques, e.g., CT and MR scanning, surface scanning and photogrammetry. These tools encompass relatively simple visualization tools to powerful instruments for performing virtual 3D crime scene reconstructions. A multi-modality and multiscale approach to a crime scene, where 3D models of victims and the crime scene are combined, offers several advantages. A permanent documentation of all evidence in a single 3D environment can be used during the investigation phases (e.g., for testing hypotheses) or during the court procedures (e.g., to visualize the scene and the victim in a more intuitive manner). Advanced computational approaches to understand what might have happened during a crime can also be applied by, e.g., performing a virtual animation of the victim in the actual context, which can provide important information about possible dynamics during the event. Here, we present an overview of the different techniques and modalities used in forensic pathology in conjunction with crime scene investigations. Based on our experiences, the advantages and challenges of an image-based multi-modality approach will be discussed, including how their use may introduce new visualization modalities in court, e.g., virtual reality (VR) and 3D printing. Finally, considerations about future directions in research will be mentioned.

Quantifying forensic investigations involving bloodstain pattern analysis within the UK

Research informed by practice is more likely to have a greater impact on society. However, forensic cases are confidential and thus, real-life data regarding the details of violent crime is usually withheld from the public and academia. Through a partnership between the authors institution and a UK police service, casefiles from 78 criminal investigations from 2012 to 2020 involving Bloodstain Pattern Analysis (BPA) were examined and quantified. The most common methods of assault and weapons used were identified as well as the frequency of different bloodstain pattern classifications. The results of this study will help inform researchers and supply forensic training providers with data derived from forensic practice. Despite a significant body of literature exploring impact patterns and software for calculating the Area of Origin (AO), impact pattern was classified at only 22% of scenes, with sharp-force trauma being the most prevalent form of assault. This paper recommends a review of the BPA terminology, to include additional commonly encountered patterns that are not defined by the current standard.