The reliability of clues in forensic firearm examinations

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Forensic firearm examination is a branch of forensic science that focuses on the analysis and comparison of firearms, ammunition and related evidence to determine their connection with a specific crime. It plays an important role in criminal investigation, especially in linking firearms with crime scenes, the identification of firearms used in criminal activities, and the provision of expert evidence in court.

The investigation process in forensic firearm analysis involves various principles and techniques. One of the key principles is the uniqueness of firearms, which means that no two firearms – even of the same make and model – will produce identical marks on fired bullets and shells / cartridge cases. This principle forms the basis for the comparison of firearm results. Firearm examiners use specialised tools and microscopes to examine and compare the striations, firearm marks and other microscopic characteristics that appear on the bullets and shells.

Critics of forensic firearm examinations question the reliability of the findings of firearm examinations and state that these examinations are not based on valid scientific research and that the absoluteness of the findings is over-represented/exaggerated.

They claim that the subjective nature of the analysis and the lack of standardisation in the field can result in mistakes and prejudice/bias in the conclusions drawn by examiners. In addition, the critics argue that there is a lack of compelling empirical studies to support the validity and reliability of the discipline.

In response to this criticism, the Association of Firearm Tool Mark Examiners (AFTE) and other experts have made a case for the reliability and validity of forensic firearm examinations. The AFTE claims that the discipline is based on sound scientific principles and is critically studied according to the prescripts of the scientific method. The AFTE stresses that there is a wealth of literature to support the validity of firearm identification and that firearm examinations can definitely link a bullet or shell to a specific firearm.

The AFTE developed the theory of identification, which serves as the published statement of the relevant scientific community. In terms of this theory, when there is a stronger similarity between individual characteristics of two biometrical marks, such as marks on bullets or shells, than between marks known to be produced by different firearms, and if there is a consistent similarity between marks known to be produced by the same firearm, the conclusion can be drawn that these marks came from the same firearm.

According to the AFTE and firearm experts, the reliability of forensic firearm examinations is corroborated by the extensive training and experience required of firearm examiners. These individuals undergo stringent training and often have years of practical experience in conducting examinations and comparisons. The experts claim that the skill involved in examinations, together with the systematic and scientific approach to analysis, guarantees the reliability and accuracy of their conclusions/findings.

It is recommended that firearm examiners avoid presenting their results in absolute terms and, where possible, quantify their findings with supporting statistics. They should communicate their findings and conclusions with a degree of caution, acknowledging the limitations and uncertainties that are inherent in a forensic firearm examination. By avoiding absolute statements, the examiners can accurately convey the significance and reliability of their findings to the court. It is also essential that court officials present firearm results together with other supporting evidence. This approach ensures that firearm evidence becomes part of the broader context of the case, which promotes a just and balanced evaluation of the evidence by the court.

Purposeful/purposive interviews were conducted with 30 detectives from 10 police stations in Gauteng, four international forensic experts from overseas institutions and five local forensic examiners by using semi-structured interview schedules. Research data was obtained by analysing existing literature meticulously, as well as by collecting data from the participants.

The results of this study provide insight into the perception of detectives and local and international forensic examiners regarding forensic examination clues, with specific reference to firearm-related results.

Keywords: class characteristics; firearm-related evidence; firearm-related striations; source attribution



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