It is interesting to hear you say that. I have wondered. Are we getting the most accurate rendering...
In certain situations, such as trials, they now try to use two translators or interpreters. Actually, they are supposed to use three, two of whom take turns while the third one supervises for accuracy and adherence to standards. However, in the translation of written documents, particularly considering the volume of documents and the small number of Arabic or Farsi translators, the work is usually done by one person (although I would suspect that a document for the NSA was reviewed and edited by more than one person).
There have been instances, including in the State Dept., of translators wilfully mistranslating or not translating, however. It's something worth noting.