This study explores interpreters' role performance, lawyers' reactions to interpreters' performance, and the perceptions and expectations of the interpreter role among these two groups of professionals. It adopts an ethnographic approach to generate data from observations made in Australia of 20 authentic interpreted lawyer-client interviews and post-observation interviews with the lawyers and the interpreters respectively. The study shows that interpreters are very active participants in lawyer-client interviews, as manifested in their various forms of intervention and in their adoption of roles not stipulated in their professional ethics. The interpreters' active performance of their role relates to their perception of their function, their understanding of the relevant communicative tasks, their assumptions about lawyer's professional needs, and their previous interpreting experience. While lawyers strongly supported an understanding of the interpreter role as "impartial and faithful" and spoke against certain types of interpreter interference, such as interpreters using summarisation, yet in actual practice, very few lawyers were observed to question or stop interpreters' interference, and the lawyers' inaction may in fact be partly responsible for the interpreters' adoption of additional roles. These findings have implications for the professional development of interpreters and for lawyers in how to conduct effective interpreted legal interviews.