What is the duty of the trial court of the sua sponte rule in criminal cases?

In criminal cases, even in the absence of a request, the trial court must instruct on the general principles of law relevant to the issues raised by the evidence. The general principles of law governing the case are those principles closely and openly connected with the facts before the court, and which are necessary for the jury's understanding of the case. (People v. Wickersham (1982) 32 Cal.3d 307, 323, 185 Cal.Rptr. 436, 650 P.2d 311.)

The sua sponte rule " '... [is] undoubtedly designed to promote the ends of justice by providing some judicial safeguards for defendants from the possible vagaries of ineptness of counsel under the adversary system....' [Citation.]" (People v. Flannel (1979) 25 Cal.3d 668, 683, 160 Cal.Rptr. 84, 603 P.2d 1.) The trial court need not fill in every time a litigant or his counsel fails to discover an abstruse but possible theory of the facts. (People v. Wade (1959) 53 Cal.2d 322, 334, 348 P.2d 116.) "The duty of the trial court involves percipience--not omniscience." (People v. Cram (1970) 12 Cal.App.3d 37, 41, 90 Cal.Rptr. 393.)