Interactions with non-English-speaking participants in legal contexts in England are normally conducted with the assistance of one interpreter. On occasion, however, more than one interpreter, or an individual (or individuals) with knowledge of the languages in question, may be simultaneously present during an interpreted interaction, either monitoring it or volunteering unsolicited input. During police interviews or trials in England this may happen for example when the interpreter secured by the defence team to interpret during private consultation with the suspect or defendant is present also in the interview room or the courtroom. By analogy to the nature of the English legal system, I refer to contexts where an interpreter’s output is monitored and/or challenged, either during the speech event or subsequently, as ‘adversarial interpreting’. This conceptualisation reflects the fact that interpreters in such encounters are sourced independently, often by opposing parties, and as a result can rarely be considered a team. My main concern in this presentation is to throw spotlight on adversarial interpreting as a hitherto rarely discussed problem in its own right. That it is not an anomaly is evidenced by the many cases around the world where the officially recorded interpreted output was challenged, as mentioned in for example Berk-Seligson (2002), Hayes and Hale (2010), and Phelan (2011). The presentation reports on the results of a research project using data from interpreter-mediated police interviews and input from practising interpreters. I will try to answer the question of how the presence of two interpreters, or an interpreter and a monitoring participant, in the same speech event impacts on the communication process. I will also address the issue of forensic linguistic arbitration in cases where incompetent interpreting has been identified or an expert opinion is sought in relation to an adversarial interpreting event of significance to a legal dispute. References Berk-Seligson (2002), The Bilingual Courtroom: Court Interpreters in the Judicial Process, University of Chicago Press. Hayes, A. and Hale, S. (2010), "Appeals on incompetent interpreting", Journal of Judicial Administration 20.2, 119-130. Phelan, M. (2011), "Legal Interpreters in the news in Ireland", Translation and Interpreting 3.1, 76-105.