This summary is not the rule. The rule text controls.
If a court case needs an interpreter, that person must first be shown to be qualified for the job. This usually means checking their language skills and training to make sure they can accurately translate what's being said.
Before they start interpreting, they also have to take an oath or affirmation. This is a formal promise to translate everything truthfully and accurately, without changing or leaving out any part of what someone says. This step helps protect the fairness of the case, since witnesses, defendants, or other people involved may rely completely on the interpreter to understand and be understood in court.
