What is the test for instructing a jury on a lesser crime?

We begin with the well-established proposition that the court's obligation to instruct on all principles of law relevant to the issues raised by the evidence at trial includes the obligation to instruct " 'on any lesser offense "necessarily included" in the charged offense, if there is substantial evidence that only the lesser crime was committed. This venerable instructional rule ensures that the jury may consider all supportable crimes necessarily included within the charge itself, thus encouraging the most accurate verdict permitted by the pleadings and the evidence.' [Citation.]" (People v. Smith (2013) 57 Cal.4th 232, 239, italics added.)