As a general rule, specific intent is not an element required to be proven under the statute. United States v. Bailey, 444 U.S. 394, 404 (1980). See also United States v. Tapio, 634 F.2d 1092 (8th Cir. 1980). However, a number of cases have required a showing of specific intent pursuant to the "law of the case." See United States v. Cluck, 542 F.2d 728 (8th Cir.), cert. denied, 429 U.S. 986 (1976); United States v. Woodring, 464 F.2d 1248, 1250 (10th Cir. 1972).
The government need not prove the existence of unlawful intent at the moment at which a prisoner or convict departs from custody. It is sufficient to sustain a conviction of escape if a person who leaves his place of confinement involuntarily or inadvertently, voluntarily forms an intent to remain at large at a later time. See Bailey, supra; United States v. Phipps, 543 F.2d 576, 577 (5th Cir. 1976), cert. denied, 429 U.S. 110 (1977); Cluck, supra, at 731; Woodring, supra, at 1250; and Chandler v. United States, 378 F.2d 906 (9th Cir. 1967).