In the adversarial legal system, the speech behaviour of witnesses can determine the outcome of the case. Studies on the language of testimony have shown that linguistic features such as pronunciation, choice of vocabulary and grammar all contribute to forming an impression of the witness or defendant on the basis of his or her perceived level of education and social class. This paper presents the findings of a study based on the analysis of eleven hours of interpreted testimony from four Local Court cases involving Spanish and English in Australia. The evidence suggests that interpreters tend to raise the level of formality when interpreting into English and lower it when interpreting into Spanish. Some suggestions are made concerning the possible motivations and implications of such practice.