What is the test for admissible evidence of an allegation made against a party under the hearsay rule?

"Evidence of a statement offered against a party is not made inadmissible by the hearsay rule if the statement is one of which the party, with knowledge of the content thereof, has by words or other conduct manifested his adoption or his belief in its truth." (Evid. Code, 1221.) "In determining whether a statement is admissible as an adoptive admission, a trial court must first decide whether there is evidence sufficient to sustain a finding that: (a) the defendant heard and understood the statement under circumstances that normally would call for a response; and (b) by words or conduct, the defendant adopted the statement as true. [Citations.]" (People v. Davis (2005) 36 Cal.4th 510, 535.)