(a) Evidence of a statement is not made inadmissible by the hearsay rule when offered in an action upon a claim or demand against the estate of the declarant if the statement was made upon the personal knowledge of the declarant at a time when the matter had been recently perceived by him and while his recollection was clear. (b) Evidence of a statement is inadmissible under this section if the statement was made under circumstances such as to indicate its lack of trustworthiness.