What is the current state of the law in cases involving insanity and insanity?

2 We indulge in the assumption that every defendant is sane, and it is not incumbent upon the prosecution to prove sanity until the defense presents evidence to the contrary. "But once substantial evidence of insanity is received in evidence, the presumption of sanity disappears. The burden is then placed upon the prosecution to prove legal sanity beyond a reasonable doubt, as in the case of any essential element of the crime charged." Hartford v. United States, 362 F.2d 63, 64 (9th Cir. 1966). See also United States v. Segna, 555 F.2d 226, 229 (9th Cir. 1977); United States v. Hartfield, 513 F.2d 254, 259 (9th Cir. 1975).