Where part of an act, declaration, conversation, or writing is given in evidence by one party, the whole on the same subject may be inquired into by an adverse party; when a letter is read, the answer may be given; and when a detached act, declaration, conversation, or writing is given in evidence, any other act, declaration, conversation, or writing which is necessary to make it understood may also be given in evidence.
(Enacted by Stats. 1965, Ch. 299.)