What is the legal test for failure to give a unanimity instruction?

^6. We note there appears to be a split in authority regarding which error standard applies for the failure to give a unanimity instruction. (See People v. Matute (2002) 103 Cal.App.4th 1437, 1448-1449 [noting that "[s]ome cases hold that the ensuing conviction must be overturned unless the constitutional error can be demonstrated to be harmless beyond a reasonable doubt," whereas "[o]ther cases find appropriate the test [is] . . . whether 'it is reasonably probable that a result more favorable to the appealing party would have been reached in the absence of the error' "].)