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Identifying the skeletal remains of an unidentified individual is a priority for the medico-legal system because identification increases the chances of finding the person responsible and provides closure to the family. The purpose of this research was to develop a combined morphological and metric cranial sex assessment method using 3D technology that accommodates the medico-legal system, and their use of 3D models facilitates the technological transition to digitally archived skeletal collections. A total of 91 individuals of European biogeographical ancestry from the William M. Bass Donated Skeletal Collection (University of Tennessee Knoxville) were imaged using photogrammetry, turned into 3D models using Agisoft PhotoScan, and digitally evaluated using 3D Studio Max. This novel method digitally evaluated five cranial traits, including the nasal aperture height, nasal aperture width, mastoid length, the general size and architecture, and the supraorbital ridges, combining techniques that can only be done digitally with those that can be completed on the actual bone. Preliminary statistical tests demonstrate an overall accuracy rate of 90% when tested against the training sample (20 males, 20 females) and 75% when tested against the test sample (51 individuals). Although no intra- or inter-observer error rate tests were done, and further testing on other skeletal collections is necessary, this method allows forensic anthropologists to perform relatively easy point-to-point measurements, the quantification of traditionally non-quantified traits, the possibility of reproducible results, and the ability for future analyses or research.

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. •The first point of contact follows a similar trend to the sine value.•The trajectory point moves along the half-length of the bloodstain.•The trajectory point and first point of contact are mainly at different locations.•The trajectory point is not always at the centre or tip of the ellipse.•The first point of contact is not always at the centre of tip of the ellipse.

The use of trajectory rods at shooting scenes to document a bullet’s trajectory is useful since the probing method provides for an immediate visual reference as to where the projectile came from and where it may have been traveling to. Trajectory rods are also quite simple to measure with manual tools. However, the use of trajectory rods is not always possible because a bullet may strike a relatively thin material, such as a metal panel, creating a bullet impact that is not suitable for determining the bullet’s path using the probing method. In these cases, it may be possible to use the elliptical method or the lead-in method. The ellipse method has been shown to have some of its own challenges when the bullet impact site is highly deformed while the lead-in method is less studied and only useful over lower ranges of impact angles. This study looks to define the lead-in method and then test its performance with 15 blind participants and 5 different calibers, each with two different types of ammunition. The results of this study have shown that each combination of caliber and ammunition has its own characteristic error curve that appears to change with the known impact angle. Errors do not remain constant and in some cases, the errors exceed 20°. The range of errors is greater at higher angles of incidence where the lead-in area is relatively small. The procedures outlined in this study propose a method of use, highlight limitations, and provide insight into the accuracy for the lead-in method. •Defined the lead-in method to measure single bullet impacts in thin metal panels.•Trajectory rods and digital angle gauges were used to measure impact angles.•Identified characteristic error patterns specific to ammunition types and caliber.•Proposed correction factors to account for predictable errors.•Increased accuracy and precision when estimating trajectory and shooter placement.

•Calculated PVE of a cast-off pattern by 17 participants fit within a box width dimension of± 15 cm.•The area of origin has shown to be useful to show an exclusion zone.•The Path Volume Envelope encompasses part of the swing path.•Swing path distance from the area of origin may be estimated in the future. The estimated volume of the swing path is referred to as the Path Volume Envelope (PVE) which defines a volume in space from which the path of a blood-releasing object is contained within. FARO Zone 3D is a software program that allows for the calculation of the PVE; however, there are no current studies which look at how well this method performs across various analysts for a simple, human created cast-off pattern. A total of seventeen participants were provided data for a single cast-off pattern that was produced from human motion using a wooden dowel rod as the “weapon”. The known three-dimensional motion of the object which created the cast-off pattern was documented using a motion capture system but remained unknown to the participants. The results show that an approximate maximum width of the PVE of±15 cm is enough to encompass the results of all participants in this study. In addition, the X, Y and Z position of the center of the PVE was found to have a standard deviation of 0.1 cm, 5.1 cm, and 9.9 cm, respectively. The standard deviations of the rotations for the PVE around the horizontal and vertical axes (i.e., yaw and pitch) were found to be 2.6° and 1° respectively. Overall, the combined results of all participants were able to fit within a rectangular prism with an overall width of± 15 cm which appears to be a reasonable value for simple scenarios, since it can define an approximate location from where an object was swung relative to a wall or another object at a crime scene. A PVE of greater or lesser maximum width may be required depending on the complexity of the cast-off pattern, the weapon used, and other factors.

•A sample set of cartridge cases was collected from various people firing the same gun and ammunition.•A proposed method used the statistical data from the sample set to estimate a shooter’s position from ejected cartridge cases.•It was found that with an increasing number of cartridge cases used for shooter position estimation, the errors and standard deviation decreased, improving estimation results. Ejected cartridge cases in shooting incidents are useful in crime scene reconstruction to approximate the location of a shooter and the dynamics of an encounter. The purpose of this study is to propose a method to approximate a shooter’s position based on a reference sample set of cartridge case ejection patterns. This research is significant as there are no blind studies that determine the precision or errors when estimating a shooter’s position based on cartridge case ejection patterns. Understanding the errors associated with shooter position estimation may give investigators a standardized method for establishing a reference set of cartridge cases which reflect the behavior of ejection patterns under controlled variables, while having a more reliable method when estimating a shooter’s position. A reference sample set of more than 312 cartridge cases was collected from various people firing the same gun and ammunition from a known position and at different heights using a double-handed grip. The proposed method used the statistical data from the reference sample set and was tested on blind data sets to determine the errors and precision using “unknown” shooters. The blind testing sets ranged between 1 and 6 ejected cartridge cases with a known direction of fire. It was found that with an increasing number of cartridge cases used for shooter position estimation, the errors and standard deviation decreased, improving estimation results. With a blind set of 6 cartridge cases, the errors were shown to average 122 cm from the known firing position. The applicability of this method depends significantly on the type of firearm, ammunition, human factors, environment and other factors.

Bullet trajectory documentation is an important part of shooting reconstructions. Manual methods are quite common, using a protractor and angle gauge, but more advanced methods using laser scanners and photogrammetry are also used for documentation. Past studies have shown that using terrestrial laser scanners (TLS) can reduce the variability in trajectory documentation. In 2020, Apple Inc. released the iPad Pro & iPhone 12 Pro with a Light Detection and Ranging (LiDAR) sensor, which effectively placed a low-cost laser scanner in mobile devices. In May of 2022, an iOS application focused on forensics called Recon-3D was released. Recon-3D uses Apple’s LiDAR sensor and fuses it with photogrammetry to produce 3D point cloud data in the e57 format. The purpose of this research was to compare the accuracy, repeatability, and quality of 3D data, using Recon-3D to the Faro Focus S350 laser scanner in bullet trajectory documentation. As a first test, twelve trajectory rods were installed on a wooden panel in a controlled, indoor environment, in order to optimize the best settings for scanning trajectory rods. Subsequently, a more practical exercise was run outdoors with a vehicle containing five trajectory rods. The mean horizontal angle error for the twelve trajectory rods installed on the wooden panel was 0.14° with a standard deviation of 0.30°. The mean error for the vertical angle was -0.05° with a standard deviation of 0.25°. For the outdoor vehicle test, the mean error for the horizontal angle was 0.03° with a standard deviation of 0.28°. The mean error for the vertical angle was 0.22° with a standard deviation of 0.36°. These errors are similar to other studies which utilize the terrestrial laser scanner with mean errors well below 1°. Although further work is required to make Recon-3D a more robust application, preliminary results are promising and in line with previous studies where the terrestrial laser scanner has been used. Thus, Recon-3D appears suitable to document trajectory rods when used in shooting reconstructions.

•New software, FARO Zone 3D includes digital tools for bloodstain pattern analysis.•Workflow and accuracy were comparable to the FARO Scene Forensic Wizard plug-in.•Majority of errors were within maximum error range recommended in past literature.•FARO Zone 3D is a suitable alternative to FARO Scene’s Forensic Wizard plug-in. This comparative study aimed to investigate the differences between the workflow, accuracy, and reproducibility of the area of origin tools in FARO Scene and FARO Zone 3D software. Released in 2018, FZ3D has recently been introduced as an alternative application to FARO Scene’s Forensic Wizard plug-in for bloodstain pattern analysis but no accuracy studies have been published at the time of this study. A total of 15 impacts were created using an impact rig at three different positions from two orthogonal walls (50cm, 75cm, 100cm). One researcher conducted the analyses with both software packages, and the total errors using FZ3D were not statistically greater than using FARO Scene (p>0.05). With FZ3D, 50% of the total errors ranged from 6.63cm to 15.68cm with a minimum of 2.45cm, maximum of 27cm, and median of 11.22cm. With FARO Scene, 50% of the total errors ranged from 3.6cm to 15.5cm with a minimum of 2.93cm, maximum of 31.25cm and median of 9.6cm. A blind test with seven participants analyzing the same 15 impacts in FZ3D resulted in 100 out of 105 total errors (95%) to be within the accepted error range of 20cm. Of the five total errors outside 20cm, one was obtained from the 75cm position and four from the 100cm position. 75% of the total errors were below 9.43cm from the 50cm position, 14.88cm from the 75cm position, and 17.39cm from the 100cm position. This could indicate that there is a positive correlation between the distance of the impact from the surfaces and total errors obtained. Based on results of previous literature and comparison to FARO Scene software, FZ3D is shown to have acceptable area of origin analysis tools.

•Single bullet impacts in thin metal are common at crime scenes.•Extrapolation of trajectory and shooter placement from these impacts is error prone.•Using the Ellipser App in CloudCompare, impact angles were measured using the best-fit ellipse method.•Preliminary results suggest single bullet impacts have characteristic error patterns from low to high impact angles.•Ammunition type has a significant effect on the error pattern. Using the best-fit ellipse method, single bullet impacts in thin sheet metal were assessed to investigate the accuracy of impact angle estimation. When a bullet passes through a metal panel, the yielding nature of metal causes changes to the metal surface and the resultant hole. This deformation of the metal complicates the assessment of single impacts using the ellipse method. Determining the correct impact angle may not be obvious and results in considerable errors between the known and calculated angle. To determine if the calculated angle varies in any particular way to the known angle, impacts were created on metal panels using six different types of 9 mm ammunition and seven angles from 90° to 14°. Impact angles, determined using the ellipse method, were compared with known firing angles and the error pattern assessed. The results show an error pattern with a significant quadratic relationship for three ammunition types, with the error pattern for the remaining three ammunitions not explained by a quadratic formula and requiring further study. Results suggest that single bullet impacts for a given type of ammunition with a quadratic error pattern, can be assessed with accuracy due to a more consistent behavior. This characteristic pattern of error requires further study but is a promising step for determining an accurate impact angle and bullet path from a single impact point in a metal surface.

Bullet trajectory documentation is an important part of shooting reconstructions. Manual methods are quite common, using a protractor and angle gauge, but more advanced methods using laser scanners and photogrammetry are also used for documentation. Past studies have shown that using terrestrial laser scanners (TLS) can reduce the variability in trajectory documentation. In 2020, Apple Inc. released the iPad Pro & iPhone 12 Pro with a Light Detection and Ranging (LiDAR) sensor, which effectively placed a low-cost laser scanner in mobile devices. In May of 2022, an iOS application focused on forensics called Recon-3D was released. Recon-3D uses Apple’s LiDAR sensor and fuses it with photogrammetry to produce 3D point cloud data in the e57 format. The purpose of this research was to compare the accuracy, repeatability, and quality of 3D data, using Recon-3D to the Faro Focus S350 laser scanner in bullet trajectory documentation. As a first test, twelve trajectory rods were installed on a wooden panel in a controlled, indoor environment, in order to optimize the best settings for scanning trajectory rods. Subsequently, a more practical exercise was run outdoors with a vehicle containing five trajectory rods. The mean horizontal angle error for the twelve trajectory rods installed on the wooden panel was 0.14° with a standard deviation of 0.30°. The mean error for the vertical angle was − 0.05° with a standard deviation of 0.25°. For the outdoor vehicle test, the mean error for the horizontal angle was 0.03° with a standard deviation of 0.28°. The mean error for the vertical angle was 0.22° with a standard deviation of 0.36°. These errors are similar to other studies which utilize the terrestrial laser scanner with mean errors well below 1°. Although further work is required to make Recon-3D a more robust application, preliminary results are promising and in line with previous studies where the terrestrial laser scanner has been used. Thus, Recon-3D appears suitable to document trajectory rods when used in shooting reconstructions. •LiDAR technology is now portable through Apple Inc.’s mobile devices which can turn into 3D scanners.•The application, Recon-3D, is tailored for 3D documentation of crime scenes.•3D documentation of bullet trajectory can be done within minutes.•An appropriate scanning technique for documenting bullet trajectories with Recon-3D is identified.•Recon-3D performs as well as the FARO Focus S350 Laser Scanner for bullet trajectory documentation.

•The majority of height measurement errors recorded were below +/- 2 cm for both methods.•The use of Reverse Projection yielded a larger range of error than PhotoModeler.•Averaging height estimates for a given suspect and distance results in lower error.•Statistical comparison of errors demonstrated higher accuracy with PhotoModeler. The purpose of this study was to compare the accuracy and precision between the Reverse Projection and PhotoModeler methods for suspect height analysis. Thirty analysts were assigned to measure the heights of three different suspects, one for each method, with the suspects having been recorded standing at three different distances in a scene. For Reverse Projection, the analysts were provided with height scales to place and video-record at the same positions their suspects stood in at the test scene, so that frames could be extracted from the video and overlaid onto frames of the suspects to measure height. For PhotoModeler, analysts calibrated frames of the suspects using 3D point cloud data obtained from a laser scan of the scene, so that measurements could be made in PhotoModeler software. Errors were calculated for the measurements and compared using the Mann-Whitney U-test and Kruskal-Wallis H-test, which indicated significant differences for errors between the two methods (p = 0.0025 and p = 0.008). Reverse Projection yielded a greater range of error and tended to have higher standard deviations than PhotoModeler, but the overall accuracy between the two methods was found to be comparable. The majority of absolute measurement errors for both methods were less than 2 cm.