What is the test for establishing a chain of custody of physical evidence?

When physical evidence is offered, the foundation is laid by establishing its chain of custody. The chain of custody is the chain of possession of the evidence to ensure that it has not been tampered with or altered. (People v. Caitlin (2001) 26 Cal.4th 81, 134.) When a chain of custody objection is made, " ' "[t]he burden on the party offering the evidence is to show to the satisfaction of the trial court that, taking all the circumstances into account including the ease or difficulty with which the particular evidence could have been altered, it is reasonably certain that there was no alteration. [] The requirement of reasonable certainty is not met when some vital link in the chain of possession is not accounted for, because then it is as likely as not that the evidence analyzed was not the evidence originally received." ' " (Ibid.)