ABSTRACT
Physical matching methods are a family of well-known methods that are utilized in order to determine whether two pieces of a tearable/breakable material used to be one object. When performing physical match of polymers, it is sometimes difficult to reach an unambiguous conclusion. This is due to various reasons. One is when the tear/fracture resides in an inaccessible or hidden-from-view region of the piece. Another is when the shape of the tear/fracture at the object's tear/fracture line is insufficient for deducing a complete match. Third is deficiency of material along this line. These are examples of processes where the line is affected so drastically, so that a match renders impossible. Specifically, when addressing elastic materials, the tear/fracture line may even be squashed. This may also be a reason for difficulty in performing a physical match. In this paper, a method is proposed where a match is alternatively achieved by means of photographic comparison of marks on the surface topography of the pieces-in-question. Comparisons of pairs of torn pieces of silicon rubber were made. The procedure involved photography of the surface topography the pieces. Then, the photographs were horizontally mirror-flipped. Lastly, a comparison was made between two photographs: a photograph of one piece and a mirror-flipped photograph of the opposite piece. The results show that after comparing the pieces to one another, only one unique pair turned out to be positively matched. Using the proposed method, not only the comparison is done by a more informative method (comparing to physical match), it is also more convenient, faster, less expensive, and technically simpler.
ABSTRACT
When receiving a stabbed tire for examination, forensic toolmark examiners can determine whether a suspect tool was used in a specific crime based on class-characteristics and individual-characteristics marks that have been left by the tool on the tire. This study discusses friction marks and their forensic value during the examination of a punctured tire. The term friction mark refers to the noticeable mark around the penetration area on a tire's surface. Tires designed to create high friction when contacting a road. Due to this design, friction is created between the stabbing tool shank and the sides of the hole. As a result of this friction, the shank of the stabbing tool wears the outer layer of tire around the hole. This leaves a friction mark whose general shape reflects the cross-sectional shape of the stabbing tool's shank. This phenomenon was observed and named by Locke (7) in his evaluation of tire puncture marks with knives. This article demonstrates the same phenomenon with other types of stabbing tools. Test stabs were produced with different tools representing a variety of cross-sectional shapes of shanks, and the resulting friction marks were photo-documented and discussed. Correlations between the various cross-sectional shapes and their corresponding friction marks are shown. Based on friction mark examination, the examiner: (i) can infer suspect tool shank cross-sectional shape with the evaluation of the friction mark shape and (ii) can deduce the maximum dimensions of the shank. This examination simplifies and accelerates the forensic comparison procedure and the investigation time.
ABSTRACT
Images and videos are common types of evidence in crime scene investigations and laboratory analysis. Images may be taken by the suspect and/or by crime scene investigators and may serve as crucial elements in forensic laboratory analysis. Forensic photographic image comparison is the process of comparing one or more objects or persons in photographs/images when at least one image is known to be related to a crime. The forensic examiner usually compares the images in order to determine whether or not an association between the exhibits in the images can be made. This paper proposes an extension to the currently prevalent photographic image examination method. The extension introduces comparison of landscape and vegetation over time. It is revealed that similarities between images may still be found between the period of time the suspect photograph was taken and the period the crime scene investigator took the photograph from the same area. In this case report, two suspects to be involved in growing a marijuana field were arrested by the police. The forensic experts were asked to examine images taken by the crime scene investigators and to compare them to the images found in the suspects' phones. They then tried to determine whether the suspects could be linked to the specific locations. While applying techniques derived from morphological comparison methodologies, the plants at the scene provided significant additional information. A tree trunk, branches, and twigs on a hedge in the photographs revealed specific individual characteristics that led the examiner to reach a conclusive decision.
