NRS 200.170: Burden of proving circumstances of mitigation or justifiable or excusable homicide.

The killing of the deceased named in the indictment or information by the defendant being proved, the burden of proving circumstances of mitigation, or that justify or excuse the homicide, will devolve on the accused, unless the proof on the part of the prosecution sufficiently manifests that the crime committed only amounts to manslaughter, or that the accused was justified, or excused in committing the homicide.