Legal Question in Criminal Law in Maryland

You can, but it will likely be denied. You may invoke your marital privilege against testifying, but you would have to do so on the record in open court. The privilege may only be invoked once.

You should let the state's attorney know that you intend to invoke the privilege ahead of time.

You may also want to get an attorney to facilitate using the privilege, because often the Assistant State's Attorney will intimidate and threaten people in an effort to make them testify. I have even seen them lie in order to attempt to get a conviction. Despicable, but true.