discussed Cited "see" United States v. Roberto Ayo-Gonzalez, United States of America v. Cuban Vessel F-V E-82hb, Her Engines, Etc., in Rem. He noted, with exhaustive citation of authority, “the principle that confessions — unlawful but not involuntary — admitted into evidence but obtained without having given the warnings required by Miranda are subject to the harmless error rule.” Id. at 432 ; accord, Null v. Wainwright, 508 F.2d 340 (5th Cir.), cert. denied, 420 U.S. 970 , 95 S.Ct. 1964 , 44 L.Ed.2d 459 (1975).