Well I used to work in the courts. A lot of people who basically speak the everyday portion of the language, get interpreters because a lot of times they won't have learned all those specialized legal terms because the only place they're used is in court.

It is not uncommon for someone to have a translator just because they're not a native speakers. If we're going to charge you, especially if you're in a potential death penalty case, we want you to understand and participate in your defense.

Maybe that's not how it works near you, but that is exactly how it works near me, the fact that he has an interpreter has no bearing on whether he speaks English or not, it just means he can't speak the language of the law in English.