Quality in interpreting has been investigated from different perspectives with the main focus being put on conference interpreting. Little research has been conducted on assessing the quality of interpreting in public service settings, more specifically, in legal settings, and in particular within police interpreting. The introduction of the Directive 2010/64/EU of the European Parliament and the European Council, which was established with the intention of strengthening language rights, was a positive development that put more emphasis on quality in legal interpreting, calling for improved quality standards along with more research into interpreting quality in public service interpreting contexts. In the United Kingdom, the introduction of the Framework Agreement for interpreting and translation services has not helped to implement the Directive. The dilution of existing standards and procedures for interpreter recruitment in the legal setting, has had drastic effects on interpreting quality and service provision. Therefore, research is imperative, especially research into factors that influence interpreting quality in public service interpreting, in order to create an evidence base. In this context, this experimental study based on simulated data examines the quality of interpreting in the police setting by analysing the performance of interpreters with different professional profiles. It seeks to determine the factors that influence the quality of interpreting and establish links between interpreters’ profiles and their performance. To achieve its aims, the study includes nine interpreters and adopts a multi-method approach, combining qualitative and quantitative empirical investigations of the interpreters’ performance (output quality) with data elicited in reflective sessions and a questionnaire-based analysis of the interpreters’ profiles. The study employs pre-experiment questionnaires that provide information on interpreters’ backgrounds, it analyses the interpreters’ performance in simulated police-suspect interviews against a set of criteria that were devised to evaluate interpreting quality in the legal context. It also employs post-experiment retrospective think-aloud protocols to gain additional insights into the interpreters’ decision-making mechanisms. Through employing a multi-method approach and by creating a model for assessing the quality in the legal settings, the present study complements and extends recent studies on police interpreting conducted by Böser (2013), Braun (2013) or Gallai (2017) and provides a better understanding of factors which influence the quality of interpreting.