The rationale for requiring courts to instruct on lesser-included offenses is to avoid forcing the jury into an ” ‘unwarranted all-or-nothing choice’ ” that creates the risk the jury will convict on the charged offense even though one of the elements remains in doubt because ” ‘the defendant is plainly guilty of some offense.’ ” (People v. Hughes (2002) 27 Cal.4th 287, 365; accord, People v. Majors (1998) 18 Cal.4th 385, 410 [“One of the primary reasons for requiring instructions on lesser included offenses is … to eliminate ‘ “the risk that the jury will convict … simply to avoid setting the defendant free.” ’ [Citation.]”]; People v. Barton (1995) 12 Cal.4th 186, 196, 203 [” ‘Our courts are not gambling halls but forums for the discovery of truth.’ ” The “jury’s truth-ascertainment function” is impaired unless it is provided with “the opportunity to decide whether the defendant is guilty of a lesser included offense established by the evidence”].)
Such instructions “encourag[e] the most accurate verdict permitted by the pleadings and the evidence.” (People v. Birks (1998)19 Cal.4th 108, 112; see People v. Breverman (1998) 19 Cal.4th 142, 161.) Moreover, we have said that a rule requiring such instructions “ensures that the jury will be exposed to the full range of verdict options which … are presented in the accusatory pleading itself and are thus closely and openly connected to the case.
Hence, the rule encourages a verdict, within the charge chosen by the prosecution, that is neither ‘harsher [n]or more lenient than the evidence merits.’ ” ( Birks , at p. 119, 77 Cal.Rptr.2d 848, 960 P.2d 1073 ; see Breverman , at p. 155, 77 Cal.Rptr.2d 870, 960 P.2d 1094 ; Barton (1995) 12 Cal.4th 186, 196.) In this connection, we have also emphasized that ” ‘[o]ur courts are not gambling halls but forums for the discovery of truth’ ” (Barton at 196, quoting People v. St. Martin (1970) 1 Cal.3d 524), “implying that an all-or-nothing choice encourages a high-risk, high-reward gambler’s approach to criminal justice.” (See People v. Hicks (2017) 4 Cal5th 203, 210.)
In People v Potts (2019) 6 Cal5th 1012 the Court again assumed that jurors may not follow the instructions and return an “erroneous conviction” when they are faced with a choice between conviction and acquittal. However, Potts in concluded that when the choice is between conviction and no decision the “risk of erroneous conviction is particularly diminished….” “We presume that jurors follow instructions. There is far less reason to doubt that they will do so when the alternative is a mistrial rather than an acquittal….”