What is the test for a jury to find that a co-principal committed attempted murder?

A rational jury would understand that the instruction required the jury to find that a co-principal committed attempted murder. The jury was correctly instructed on the elements of attempted murder and premeditated attempted murder necessary to convict a defendant of those crimes, including the requisite intent. There is no reasonable likelihood that the jury understood the instruction to permit it to convict defendant of attempted murder without finding that a principal actually committed attempted murder, and did so with the necessary element of intent. To use defendant's formulation of the Chapman¹⁰ standard of review, the error did not contribute to the verdict and was harmless beyond a reasonable doubt. (See People v. Patterson (1989) 209 Cal.App.3d 610, 615.)