The role of a firearm examiner is wide ranging, involving tasks that require scientific understanding in aspects of chemistry, physics and biology. This article aims to provide a critical review of the key scientific principles and practices specifically involved with forensic firearm identification and to discuss how misidentifications have resulted in cases of injustice. Implementation of quality assured examination practice, demonstration of individual examiner competence and more objective methods of reporting are being adopted by firearm examiners and laboratories to address some of the criticisms relating to subjectivity and standardisation inherent within the discipline. The impact of these changes is outlined and further recommendations are made for both examiners and legal professionals to minimise the potential for future injustices involving firearms evidence. Latest research in the field is cited, continuing to support the theory and use of firearm identification as admissible evidence in court.