The setting is New Mexico in 2007—the date being the major stumbling block with just searching for this on Google, since I'm mostly trying to avoid anachronism here.
I have one character who is a disgraced FBI agent trying to interrogate a suspect while on the move from bigger bads (so sitting down at a computer and typing things out is not an option; they're mostly in a car making stops). The catch is that the suspect is mute. He is generally able to get by in his daily life without talking to anyone; he carries a pen and paper around for when aggressive gesturing doesn't cut it.
Since they're mainly driving, having them pass notes back and forth isn't the best way to communicate tons of information, especially since under other circumstances they're both incredibly wordy. Were it today, I'd have them use a text-to-speech app on a cellphone, but from what I remember, that wasn't a commonly available feature back then. I have vague memories of an ESL classmate who had a portable translator of some sort, but again, I don't know how common those were.
Any ideas for how to give my voiceless character (temporarily) a voice?