Train of Dreams (1987)

A teenage boy in juvenile detention is inspected while fully nude to check for contraband. There is a clear but fairly brief view of his naked body, including his penis, scrotum, and pubic hair. He turns around and bends over, and his butt is clearly visible. A guard tells him to "spread em'," implying that he has to spread his butt cheeks, but this isn't shown. This is not in a sexual context.