Can a witness’s own statement be hearsay?

Yes.  If a witness testifying at trial made a prior statement that a party would like to introduce and that statement was intended as an assertion and is now being offered as substantive evidence to prove the truth of the matter, then the statement would still be hearsay.  It is immaterial whether or not the witness is present in court to be cross-examined with respect to the earlier statement.

Hearsay is an out-of-court declaration that is offered to prove the truth of the matter asserted. Hearsay can be oral or written. It can also behavioral (for example, pointing).  Any evidence that does not satisfy all three conditions – out-of-court, assertion, offered for the truth – is not hearsay.

Because a witness’s own statement from a previous occasion satisfies all three conditions, it is hearsay. Therefore, it can only be admitted pursuant to a valid exception to the hearsay rule.  It might come in, for example, as an excited utterance, present sense impression or as a prior consistent or inconsistent statement.