I will hear thy cause (diakousomai). “I will hear thee fully” (dia).
When--are come (paragenōntai). Second aorist middle subjunctive of paraginomai with temporal conjunction hotan, indefinite temporal clause of future time (Robertson, Grammar, p. 972), “whenever thine accusers come.”
In Herod’s palace (en tōi praitōriōi). The Latin word praetorium. The word meant the camp of the general, then the palace of the governor as here and Mat 27:27 which see, and then the camp of praetorian soldiers or rather the praetorian guard as in Phi 1:13.