What is the test for unanimity in a case involving possession of drugs for sale?

It is well established that the jury's verdict in a criminal case must be unanimous. (People v. Russo (2001) 25 Cal.4th 1124, 1132 (Russo).) "Additionally, the jury must agree unanimously the defendant is guilty of a specific crime. [Citation.] Therefore, cases have long held that when the evidence suggests more than one discrete crime, either the prosecution must elect among the crimes or the court must require the jury to agree on the same criminal act. [Citations.]" (Ibid.)

"This requirement of unanimity as to the criminal act 'is intended to eliminate the danger that the defendant will be convicted even though there is no single offense which all the jurors agree the defendant committed.' [Citation.]" (Russo, supra, 25 Cal.4th at p. 1132.) "[S]uch an instruction must be given sua sponte where the evidence adduced at trial shows more than one act was committed which could constitute the charged offense, and the prosecutor had not relied on any single such act. [Citations.]" (People v. Dieguez (2001) 89 Cal.App.4th 266, 274-275.)

In cases involving prosecution for possession of narcotics for sale, a unanimity instruction is required when (1) "actual or constructive possession is based upon two or more individual units of contraband reasonably distinguishable by a separation in time and/or space"; (2) "there is evidence as to each unit from which a reasonable jury could find that it was solely possessed by a person or persons other than the defendant"; and (3) the prosecutor did not elect to rely on only one of the individual units. (People v. King (1991) 231 Cal.App.3d 493, 501-502 (King).)