So, we have state-level certification and federal level certification for court interpreters. Certifications are also only offered in very few languages.
So, can you take a state court interpreter into a federal court hearing? I have seen this, especially in civil cases and never in a criminal case. It is still risky to do it. You may be able to get away with it for federal court FLSA mediations and civil hearings where opposing counsel is somewhat amicable. But, however you look at it, you are taking a big risk. Other than FLSA settlement conferences I would suggest as a general rule of thumb, always use a federal court certified interpreter for all federal cases requiring a Spanish interpreter.
Spanish is the only federal court certified language that has a good long list of interpreters. All other languages have been discontinued, meaning you can use any qualified interpreter (the term “qualified” is arguable in this case and is very much up to the judge).
So what about the inverse? Can we use a federal court interpreter in state court proceedings?
Qualifications wise, the interpreter will be able to handle it, no problem. The way the state and federal exams work are very similar, just that the federal exam is much harder.
But the issue may be that local regulations may stop a federal court interpreter that is not state-certified from interpreting at state proceedings. Recently, the State of Florida has created rules requiring interpreters to be State certified. Some judges seem to not go by these rules and instead use a practical approach and allow practically anyone (certified or not) to interpret, as long as there is no objection from the parties.