Forensic Investigation of Bullet Holes for Determining Distance from Glass Fracture Analysis

The study of glass fracture patterns has been of long interest to the forensic community. Fragments of glass can be significant evidence found in the investigation of various types of offenses especially where armed violence is involved on automobiles. Figuring out, whether glass fragments present on crime scene share the same origin as per glass that has been hit by a projectile or any substrate, is quite a success to an examiner because that further leads to the investigation of how and by which means it has done. Holes occurred in the glass at the crime scenes have much importance and many attempts are taken to investigate the properties of these glass holes to find the type, speed, and angle of the projectile which probably produce the hole. For highvelocity projectiles including bullets, these bullet holes in glass can exhibit certain features and fractures. The objective of this research was to determine the distance of shooter from the bullet hole on glass used in automobiles. Bullet holes were prepared and different parameters of glass fractures like bullet hole diameter, cone fractures radius, cone fractures diameter, radial, and concentric fracture count were considered from both front and the backside of the glass. These parameters were observed and analyzed to determine the dependency of these parameters on the variable “distance”. The consistency found in the measurements to conclude our results were checked by goodness of fit test. The study bears great significance as it could lay down a foundation to set a standard parameter to estimate distance of bullet hole from shooter in firing incidents involving glass fracture. This will provide a blueprint to crime scene investigators in order to reconstruct the crime scene for understanding and to take investigation to logical conclusion.

Fracture phenomena of float glass measured by the quasi-static method

Glass fracture and changes in bending load were investigated by the quasi-static loading method which is characterized by holding a fixed time at each displacement level and incrementally applying displacement. Holding time at each step was 60 s and the incremental displacement was 0.02 mm as the load condition. Ordinary soda-lime-silicate float glass of 50 × 10 × 4 mm was used as the specimen. The glass fracture occurred as the bending load decreased with time, which might be explained using the occurrence of time-dependent fracture and function as a viscoelastic property even at room temperature. Fracture properties of alumina ceramics have the possibility to be closer to float glass than silicon carbide which is called general ceramics.

Glass Fracture during Micro-Scratching

The regularity of glass surface fracture and resistance to destruction were investigated by the methods of progressive and static microscratching with the Berkovich indenter. The research hardware was the original nanoindentation/microscratching devices and a non-contact interference profilometer for studying the morphology of the formed microscratches. The regularities of the fracture stages and the cracks growth along the microscratch were established depending on the indenter applied load. Based on analysis of the microcracks profile formed at various loads on the indenter immediately after the process of applying these scratches and after several hours of rest, it was found that the process of crack propagation along the scratch continues for a long time. Taking into account this established fact, a discrete-statistical method of the cracks formation for a long time is proposed. In accordance with this method, scratching is carried out with a constant load on short and separated tracks. The load on the indenter in each track increases discretely with a certain step. The influence of the medium on the scratching process is analyzed. The breaking mechanism in the glasses scratching process is formulated as the load on the indenter increases, and a model of the glass fracture stages is proposed.

The effects of crossbow impacts onto a common automotive vehicle side window—a preliminary study

In recent times, the number of criminal incidents involving crossbows in the UK has increased with many incidents resulting in either injuries or fatalities. Whilst the effects of crossbow bolts on the body are well understood, there is a limited understanding on how these projectiles interact with the wider environment. One area of particular interest is the interaction between common vehicle side windows and bolts. In this study, the penetrability of two distinct bolts using an off-the-shelve crossbow against a common automotive side window was explored, where velocity loss up to 25 m/s post impact was recorded. All windows failed through radial glass fracture at a rate up to 1600 m/s, whilst bolt damage varied from tip holder decoupling, shaft damage, and traumatic fletching removal. No distinct relationship between bolt type, velocity, and window damage was identified.