Interpreters have an ethical responsibility to maintain the legal equivalence of the source language (SL) in the target language (TL), which means reproducing the speaker's language level, style, tone, and intent in the target language. In the bilingual immigration hearings analyzed for this research, interpreters altered the courtroom reality through a variety of linguistic mechanisms: inaccurate use of discourse markers, inaccurate lexical choice, alteration of verbs and verb tenses, and the inaccurate use of repetitions. Despite their efforts to interpret unknown lexicon or expressions, interpreters often failed to maintain legal equivalence in the target language. This study examines the impact of five immigration interpreters on eleven Spanish-English bilingually conducted hearings in a federal immigration courtroom. Their performance is analyzed using conversational and discourse analysis techniques to identify linguistic strategies they employ as repair mechanisms when confronted with both semantic and pragmatic challenges. The data show that the interpreter's linguistic choices often altered the defendant's testimony, sometimes damaging his or her credibility and potentially affecting the outcome of the case. The interpreter's version of the testimony, as rendered in English, is the official version, the one that will be used to reflect on the defendant's innocence or guilt. The interpreter's inaccurate lexical choices changed the pragmatic force intended by the speakers and violated the ethical standards for interpreters set forth by the Federal Judicial Center.