What is the test for failing to object to an expert witness at an appeal?

"' "An appellate court will ordinarily not consider procedural defects or [alleged] erroneous rulings, in connection with relief sought or defenses asserted, where an objection could have been, but was not, presented to the lower court by some appropriate method . _ The circumstances may involve such intentional acts or acquiescence as to be appropriately classified under the headings of estoppel or waiver . _ Often, however, the explanation is simply that it is unfair to the trial judge and to the adverse party to take advantage of an error on appeal when it could easily have been corrected at the trial."' [Citation.]" (People v. Saunders (1993) 5 Cal.4th 580, 589-590.)^[16]

A. Failure to Object to an Expert Witness