Under what circumstances is waiting for another sovereign to complete their proceedings against a defendant a justifiable reason for delay under the Sixth Amendment's Speedy Trial Clause?

QUESTION PRESENTED After indicting Mr. Garcia on federal charges, the government delayed bringing him into federal custody for 23 months as it waited for the completion of his state prosecution. Employing an ad hoc approach, the Tenth Circuit determined the government’s reason for delay was valid and did not violate Mr. Garcia’s Sixth Amendment speedy-trial right. The Third Circuit has held that such a reason for delay is per se invalid, while the Fourth Circuit has deemed it per se justifiable. Thus, the question presented is: Under what circumstances, if any, is waiting for another sovereign to complete their proceedings against a defendant a justifiable reason for delay under the Sixth Amendment’s Speedy Trial Clause? i