What is the test for a conviction of conspiracy to commit murder?

Cooks, Green, and Simon argue that the evidence was insufficient, as a matter of law, to support their convictions of conspiracy to commit murder. For an appellate court to sustain a conviction of conspiracy to commit a crime, there must be substantial evidence that (1) the defendant and at least one other person agreed to commit a crime (Pen.Code, 182, subd. 1); (2) one of the alleged overt acts was committed by one of the conspirators in furtherance of the conspiracy (Pen.Code, 184, 1104); ⁶⁷ and (3) the conspirators had the specific intent to (a) agree or conspire and (b) commit the offense that is the object of the conspiracy (People v. Horn (1974) 12 Cal.3d 290, 296, 115 Cal.Rptr. 516, 524 P.2d 1300; People v. Backus (1979) 23 Cal.3d 360, 390, 152 Cal.Rptr. 710, 590 P.2d 837).