I’ve tried to analyze what goes on in my head through the process, and I haven’t been able to come to a final conclusion.

My best guess is this: it’s not a “switch”… you don’t switch to English, listen, switch to Spanish, speak… it’s more like “two” switches – one for listening, one for speaking -, or rather no switches at all, where your mind is generating thoughts/visuals/etc of what you hear and your mouth is just expressing those thoughts in the target language.

The process itself could be quite stressful, especially if you’re not an expert in the field or if there are additional distractions (like the pressure of being in a courtroom or the fact that lives/futures depend on your interpretation). It’s especially stressful, though, if you can’t understand the speaker because of their accent.

One time I was interpreting for someone who said “we need a new bus”, but because of his accent, I interpreted it as “we need a new boss” (and his boss was sitting in front of him!).

In terms of mistakes, interpreters, especially experienced ones, will easily acknowledge, correct and move on when they make mistakes. Interpreters, in my experience, will rarely forget a mistake, but they will not dwell on it at least until the job is done.

One final comment… interpreters, especially liaison or consecutive interpreters (and especially in a court setting where there’s so much at stake), have the opportunity (and responsibility) to ask for clarification if something was not understood properly, as what matters the most is that the message is relayed accurately.

Sorry about the long comments. :)