Bullet Trajectory after Impact on Laminated Particle Board

When reconstructing a bullet's trajectory prior to impact using the spatial orientation between two consecutive bullet defects (e.g., by probing), it is important to take the bullet's deflection into account. The (critical) ricochet angles as well as the vertical and horizontal deflection angles of eight cartridge types on laminated particle board have been studied. For all eight of the cartridge types combined, the critical ricochet angles lie between approximately 14° and 26°, while for the subgroup of the jacketed bullets, this range lies lower, between approximately 14° and 18°. The data from this study can be used to assess the accuracy and precision of the applied method. The results show that the highest deflection angles are seen near the critical ricochet angle. Generally speaking, vertical and horizontal deflection angles can almost be neglected above angles of incidence of 30° or 40° for handgun ammunition when shooting at laminated particle board.     

Accuracy and Reproducibility of Bullet Trajectories in FARO Zone 3D

With three-dimensional (3D) laser scanning technology and software packages, the practice of documenting and measuring bullet trajectories has benefited from greater accuracy and reproducibility. This study investigated the accuracy and reproducibility of the bullet trajectory tools in the software package, FARO Zone 3D (FZ3D). Twelve participants were provided laser scanner data for 21 bullet trajectories on drywall panels with impact angles between 25° and 90°. When the impact plane was manually aligned by the operator, 75% of the absolute errors were within 0.91° and 0.98° for the azimuth and vertical angles, respectively. The vertical angle improved to 0.47° when impact plane alignment was taken with respect to gravity (no operator influence). Thus, manual alignment is shown to be subject to greater error than alignment with gravity. However, this study shows that the accuracy and reproducibility of the FZ3D bullet trajectory tools to be comparable with previous research studies.     

An evaluation of measurement uncertainty of trajectory angles using a 3D laser scanner

Measuring trajectory angles of bullet defects at a crime scene is an important part of crime scene investigation as these angles can be used for shooting incident reconstructions. The Washington State Patrol Crime Scene Response Team (WSP CSRT) had a desire to report and use measured trajectory angles. To report quantitative measurements, a statement of uncertainty for the measurement must also be reported due to an accreditation requirement through the ANSI National Accreditation Board (ANAB), through which the WSP CSRT is accredited. This evaluation examined the measurement uncertainty of the 3D laser scanning method that the WSP CSRT utilizes for measuring the vertical and azimuth angles from trajectory rods fitted to bullet defects. Three studies were performed which examined the variation of vertical and azimuth angle measurements from trajectory rods on flat surfaces, the variation of azimuth angle measurements from a trajectory rod on a curved surface, and a traceability study with known vertical and azimuth angle measurements. Seven common substrates were selected as target materials and were shot with 9 mm Luger and 0.45 Auto caliber bullets. A vehicle with one bullet defect was utilized for the curved surface study. The WSP's current fleet of Trimble X7 3D laser scanners, the WSP Criminal Investigation Division (CID) Detectives who operate these scanners, and the Forensic Scientists responsible for trajectory rod placement and angle measurements were utilized. An overall measurement uncertainty of +/− 2.6 degrees at an approximate 95% confidence interval was determined for all trajectory angles measured from trajectory rods.     

Accuracy and Repeatability of Trajectory Rod Measurement Using Laser Scanners

Three‐dimensional (3D) technologies contribute greatly to bullet trajectory analysis and shooting reconstruction. There are few papers which address the errors associated with utilizing laser scanning for bullet trajectory documentation. This study examined the accuracy and precision of laser scanning for documenting trajectory rods in drywall for angles between 25° and 90°. The inherent error range of 0.02°–2.10° was noted while the overall error for laser scanning ranged between 0.04° and 1.98°. The inter‐ and intraobserver errors for trajectory rod placement and virtual trajectory marking showed that the range of variation for rod placement was between 0.1°–1° in drywall and 0.05°–0.5° in plywood. Virtual trajectory marking accuracy tests showed that 75% of data values were below 0.91° and 0.61° on azimuth and vertical angles, respectively. In conclusion, many contributing factors affect bullet trajectory analysis, and the use of 3D technologies can aid in reduction of errors associated with documentation.     

Utilization of X‐ray Computed Tomography for the Exclusion of a Specific Caliber and Bullet Type in a Living Shooting Victim

A bystander claimed to have been shot by a police officer, and CT scans were used to match qualitative and quantitative aspects of the unremoved bullet with police issued 9 mm Luger ammunition. CT scan methodology proved a valid approach for the measurement of bullets based on calculated measurement capability and correlation with “gold standard” physical measurement by vernier caliper. Measurements regarding length and base diameter, as well as length/diameter ratio, were insufficient to unambiguously identify a specific caliber, or a bullet of specific mass within a caliber class. It was, however, possible to exclude a bullet of specific design and mass with well‐characterized precision and accuracy values under selected CT scan conditions. A 9 mm Luger bullet (115 gr FMJ RN) was excluded from involvement in a shooting based on qualitative bullet shape combined with length, base, and ratio measurements of the bullet in‐situ for the victim.     

Ricochet of AK bullets (7,62 × 39 mm) on concrete and cement surfaces; a forensic-based study

The ricochet behaviour of AK bullets (7,62 x 39 mm) on two different concrete samples (rough and a cement-skimmed intermediate) and one cement sample were explored in this study. The estimated critical angles for these surfaces were shown to be 10.8° and 11.1° for the rough and intermediate concrete surfaces and 13.2° for the cement surfaces. In all occasions, fragmentation of the bullets was observed upon reaching critical angles. The results from the concrete surfaces highlighted the sensitivity of AK bullet ricochet angles from concrete surfaces with a different surface roughness and composition. Almost all resulting ricochet angles for the more frangible cement surfaces were observed to be much higher than currently reported literature would suggest. Consistent bullet wipe markings were observed on most samples, acting as a strong indicator for the directionality of the projectile during ricochet. Interestingly for the cement surface, a clear relationship was reported between the angle of incidence and the depth of the crater produced. Ultimately, this study highlights the potential uncertainties and possible errors that could occur in bullet trajectory determination from ricochet marks for this bullet and target combination if theoretic interpretations alone are used. There is no substitute for bullet and surfacespecific practical trials if the most accurate shooting scene reconstructions are to be carried out.     

Ricochet Behavior on Glass—Critical Ricochet Angles,Ricochet Angles,and Deflection Angles

For shooting scene reconstruction purposes, knowledge about the ricochet behavior of bullets provides valuable information. In this study, the critical ricochet angles of four cartridge types were established on plain float glass. The estimates of the critical ricochet angles varied between cartridge types and were 21.0° for .32 Auto FMJ bullets, 15.8° for 9 mm Luger FMJ bullets, 17.6° for .45 Auto FMJ bullets, and 21.3° for 9 mm Luger, Action NP bullets. The corresponding ricochet and deflection angles per incidence angle varied depending on the state of the ricocheted bullets. The mean ricochet angles are always lower than the corresponding angles of incidence, and the mean ricochet angles for the FMJ bullets with undamaged jackets are lower than those of bullets where the jacket is either damaged or the bullet partially ricocheted and partially perforated. Mean ricochet angles are lower for undamaged FMJ bullets than for undamaged Action NP bullets.     

Estimating Projectile Perpendicular Impact Velocity on Metal Sheet Targets from the Shape of the Target Hole

Abstract:  The correlation between bullet hole shapes in metal and projectile impact velocity was examined. A series of shots were fired from an M-16A1 assault rifle of 5.56 mm caliber toward a 1-mm thick metal target. All shots were fired at a perpendicular angle to the metal sheets, and the velocity was measured just before the projectile hit the target. Velocities ranged between 400 and 900 m/sec. From the replica of the shooting hole, a perpendicular plane was created, showing the symmetrical properties of the hole. The best mathematical equation describing the shape of the entrance hole was the exponential function in the form:
The empirical equation of the hole defined using the regression method is:
This equation describes the general shape of shooting holes created by velocities ranging from 440 to 750 m/sec. From this equation, one can estimate the bullet velocity when it hits the target.     

An Empirical Study on the Relation Between the Critical Angle for Bullet Ricochet and the Properties of Wood

The properties of a bullet, an object, and the incidence angle determine whether the bullet will penetrate, perforate, or ricochet. In this study, the critical angle for ricochet was established for .32 Auto and 9 mm Luger bullets on Abachi, Southern Yellow Pine, Beech, and Ipe wooden boards. Results show that the critical angle differs depending on caliber and wood type. The critical angle is higher for .32 Auto bullets than for 9 mm Luger bullets and increases with increasing wood density and Janka hardness. The established critical angles for ricochet on the lightest and softest wood (Abachi) are 10.4° and 10.3° for .32 Auto and 9 mm Luger, respectively. For the heaviest and hardest wood (Ipe), the angles were 45.0° and 33.4°, respectively. The combined results on the four tested woods show a strong linear relationship between both the density and the hardness and the critical angle for both calibers.     

The systemic error in the vertical component of handgun bullet trajectory reconstructions

Establishing the path or trajectory of a fired bullet is an often recurring part of shooting incident reconstruction. The current study describes how gravitational pull causes a systemic error on the vertical component of a trajectory reconstruction. Bullet drop, drop angle, and vertical offset are explained and calculated for 10 different handgun/ammunition combinations over a range of distances up to 100 m. The presented results are intended to provide forensic firearm examiners with a reference frame for the magnitude of error introduced on handgun bullet trajectory reconstructions over distance. Threshold values of 20 and 30 m are proposed as conservative distances up to where bullet trajectories can be modeled as straight lines with subsonic/transonic handgun bullets and with supersonic handgun bullets respectively. Both the bullet drop and vertical offset will be below 5 cm at these distances for those categories. The drop angle will be below 0.3°.     

Morphology of bullet wounds when using police ammunition, type QD-P.E.P

6 years after introduction of the police ammunition QD-P.E.P. (9 mm caliber), 9 bullet wounds are presented from forensic investigations along with the results of experimental shots at pig carcasses. The evaluation reveals the characteristic pattern of such bullet wounds: a skin defect which is almost as large as the caliber and has a sharp-edged border thus looking like it has been punched out; the contusion ring ("abrasion ring") is conspicuously narrow. These findings can be explained by the shape and design of the projectile. In regular police work immediate incapacitation has not always been achieved, depending on the entry location of the bullet. Experimental shots at pig carcasses showed that in the case of shots at extremities, the residual energy of the exiting bullet may be sufficient to generate another penetrating bullet wound.     

Behavior of expelled glass fragments during projectile penetration and perforation of glass

Bullets striking common forms of flat glass with an orthogonal intercept angle result in a cloud of ejected glass fragments that are in concert with the exiting bullet's flight path. This is not the case with strikes at angles other than orthogonal. In these situations, the expelled glass fragments follow a very different course from that of the exiting projectile. This is both counterintuitive and a potential source of serious error in the evaluation and reconstruction of a shooting victim's position and orientation at the moment the victim was struck by a bullet that has passed through a nearby source of glass such as a vehicle side window or a window in a building. The flight path of the ejected glass fragments is, however, predictable and is dictated by the orientation of the plane of the glass opposite the projectile's impact site.In all cases, these expelled glass particles have considerable velocity and can produce pseudostippling of the skin in individuals located downrange of bullet-struck glass and near the projectile's exit site. The distribution and location of such pseudostippling and its relationship to the associated bullet hole in glass have important reconstructive value. A proper and reliable reconstruction of the victim's position in such cases will require the integration of scene information with the autopsy findings.     

Estimating the shooting distance of a 9-mm Parabellum bullet via ballistic experiment

We demonstrate here how the shooting distance of a 9-mm Parabellum FMJ bullet (115gr) has been estimated via shooting experiments. Such a bullet was found by investigators near a concrete wall, fairly distorted at its tip. The bullet carries no evidence of multiple impact and no evidence of ballistic impact on the wall has been reported. We estimated the impact velocity by comparing the questioned bullet with a set of comparison bullets hitting a wall (rigid target) with different velocities. The shooting distance was recovered from the impact velocity by studying the typical behavior of a manufactured 9 mm bullet weighting 115 g (7.45 g), shot in pistol or a sub-machine gun. The results demonstrated that the questioned bullet was a lost bullet. The shooting distance also helped the investigators, narrowing the range of the estimated positions of the shooter.     

Accuracy in determining long-range firing position of gunman

Treating the example of a 9 mm Parabellum bullet, the paper deals with the problem of shot distance determination at long ranges. It discusses the effects of inaccurately known angles of incidence as well as of weather and ammunition data and shows that the results of computations can only indicate a certain limited area as the possible position of the shooter.     

A blind trial evaluation of a crime scene methodology for deducing impact velocity and droplet size from circular bloodstains

In a previous study, mechanical engineering models were utilized to deduce impact velocity and droplet volume of circular bloodstains by measuring stain diameter and counting spines radiating from their outer edge. A blind trial study was subsequently undertaken to evaluate the accuracy of this technique, using an applied, crime scene methodology. Calculations from bloodstains produced on paper, drywall, and wood were used to derive surface-specific equations to predict 39 unknown mock crime scene bloodstains created over a range of impact velocities (2.2-5.7 m/sec) and droplet volumes (12-45 microL). Strong correlations were found between expected and observed results, with correlation coefficients ranging between 0.83 and 0.99. The 95% confidence limit associated with predictions of impact velocity and droplet volume was calculated for paper (0.28 m/sec, 1.7 microL), drywall (0.37 m/sec, 1.7 microL), and wood (0.65 m/sec, 5.2 microL).     

An empirical study on the close-range post-ricochet orientation of AK bullets (7.62 mm × 39 mm)

Most of the injuries and deaths from ricocheting bullets in shooting incidents are usually reported due to misaimed shots that had ricocheted close to the victims. Although the destabilisation of ricocheted bullets during their ricochet flights is a generally known phenomenon, no significant quantitative-based scientific studies have attempted to understand bullets’ post-ricochet orientations at close distances. This empirical study explores close-range post-ricochet orientations of AK bullets (7.62 mm × 39 mm) on a range of domestic surface types typically encountered during bullet ricochet incidents. This study has revealed that ricocheting AK bullets off of various wood types and tile samples produce side-on impacts into closely located targets following a rightwards yaw action. It has also been shown that AK bullets ricocheting off concrete and cement samples at 5-degree incident angles produced nose-forward impacts on paper witness screens, similar to an orthogonal impact of a direct-fired shot. The findings present important new information on the post-ricochet yawing behaviour of AK bullets, which has the potential to aid future shooting reconstructions in which victims are hit by closely ricocheted bullets.     

A shot through the window

At issue in this case was whether an unusual window defect seen in two of the crime scene photographs was due to a bullet and if so, if that same bullet fatally wounded the victim. The window appeared to have been cracked prior to the apparent shot through it. A .22 bullet recovered from autopsy, when examined only by light microscopy, failed to show associated glass fragments. A previously cracked test window was shot a number of times with .22 caliber bullets near the cracks in an effort to simulate the window defect seen in the crime scene photographs. Several of the defects produced by the test window shots appeared similar to the crime scene window defect. The .22 bullet taken from the victim and several of the test bullets (collected by a cotton box) were examined by scanning electron microscopy/energy dispersive X-ray spectroscopy. The test bullets showed glass particles on and embedded in their surfaces. Particles of similar size and composition were found embedded in the surface of the bullet from the victim. The bullet likely struck the window prior to hitting the victim. It was apparent by the morphology of some of the mushroomed test .22 bullets that they hit the window crack. These bullets showed that the glass on one side of a crack often fails before the other side during the strike. Aggregations of powdered glass on many of the mushroomed surfaces of the .22 bullets suggest that as the bullet mushrooms during impact on the window surface, the glass in contact with the bullet powderizes and coats the mushroomed surface of the bullet with a layer of fine glass particles.     

Application of lead isotope analysis in shooting incident investigations

A study was conducted to examine the potential of the considerable variability of the lead isotope compositions in bullets (projectiles) and primers in shooting incident investigations. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICP/MS) was used to analyze lead isotopic compositions in projectiles, cartridge cases, firearms discharge residues (FDR) in barrels of firearms and in the gunshot entries. .22 caliber plain lead and plated ammunition and 9 mm Luger full metal jacket (FMJ) ammunition were employed in shooting experiments using semiautomatic pistols. Cotton cloth served as the target material and two firing distances were tested; 1 cm (near contact) and 2 m distances. It was observed that various mechanical or chemical means of cleaning do not completely remove lead deposits ("lead memory") from barrels of firearms. Nonetheless, it was shown that analysis of lead isotopic composition may provide valuable evidence in investigating specific scenarios of shooting incidents. For instance in a shoot-out where several firearms and ammunition brands are involved, it may be feasible to point out which ammunition and/or firearm caused a particular gunshot entry if the ammunition brands involved (bullets and primers) differ considerably in their lead isotopic composition.     

Time periods of GSR particles deposition after discharge-final results

The elemental objects of the research study are: determination of time periods corresponding to gunshot residue particles (GSR) deposition after the shot from selected pistols and a revolver, and evaluation of the deposited particles number. For several shooting experiments were used a pistol CZ model 85, caliber 9 mm Luger with common ammunition 9 mm Luger FMJ Sellier & Bellot, a pistol CZ model 70, caliber 7.65 mm Browning (32 ACP) with common 7.65 mm Browning FMJ Sellier & Bellot ammunition and a revolver S&W Modell 60, barell length 2-1/8', cal. .38 Special with common Sellier&Bellot (FMJ) ammunition. The results of the study have indicated the behavior of GSR particles deposited after a single discharge. The overall time interval of GSR particles deposition and the number of deposited particles with the above mentioned arms and ammunition were established. The results can potentially be used for clarifying the situation at crime scenes and for subsequent interpretation of GSR evidential value in caseworks.     

Forensic Significance of Gunshot Impact Marks on Inanimate Objects: The Need for Translational Research

Wherever an impact mark is found, either on the surface or on the recovered projectile, it is important for forensic investigators to extract useful information in solving shooting-related cases. This article reviews a collection of works on examination of impact marks upon striking of projectiles on inanimate objects, emphasizing on the retrievable information from a shooting scene and their forensic significance in shooting event reconstruction. Literature suggested that impact marks on target surfaces and the degree of deformation on striking projectiles vary according to different combinations of ammunition and surface materials. It was noted that conditions in real-case scenarios further differed unpredictably in comparison with controlled studies, where forensic investigation should be treated as case-specific basis. Furthermore, the way forensic science is researched and applied operationally has to be reconsidered to reduce the gap via translational approach for more effective use of forensic evidence.