The US/State attorney might step in if there is enough proof for misconduct especially if the DA cannot be trusted to handle the case impartially.
Other than that the normal appeal process is still accessible they can appeal to Courts of Appeals which is split to 12 regional circuits so this would technically allow you to get judged "out of state" not sure how far it is, or if you can appeal to be judged in another circuit.
Normally there isn't a way for people to be judged out of state mostly because they are judged according to state and local laws which can't be upheld by a different court unless the case is federal and then they go through the federal court system. And there isn't really another way for this process to work the defendant can't be expected to be able to choose where they'll be tried because it basically allows them to choose how they will be sentenced or even if they have committed a crime in the first place.