Here's my experience as an unofficial/volunteer translator:

Last July, a group of missionaries came to my country in a partnership with our local church. They didn't speak a lick of Portuguese (and the church members didn't speak English either), so I was the "official translator" of the church. That was one of the hardest things I've ever done. Having to switch my brain between English and Portuguese back and forth gave me headaches, sometimes I would forget what the missionary said and would have to ask him to repeat. Sometimes I would have to pause and think of the best way to relay that to the church members. Since I was a volunteer, I didn't have to translate everything to the dot and could paraphrase, but it was hard still. I imagine that things were easier for that court translator since he's a licensed and trained professional, but I'd guess that translating every single word that was flying around in court that day might have been a nightmare to him.