I am often asked for guidelines to translate documents to submit to the courts. Rather than write my own explanation, I will provide resources to two authoritative sources:
Guide to Translation of Legal Materials, prepared by the Professional Issues Committee of the Consortium for Language Access in the Courts in 2011. This document lists details such as how to certify a translation, how to choose the right translator, typographical conventions, just to name a few.
King County Written Language Translation Process Manual: a similar guide specific to King County, Washington State.
These guides should answer most questions about how to submit a translation to the courts and how to choose the right translator for the job.