2009 California Evidence Code - Section 710-712 :: Chapter 2. Oath And Confrontation

710.  Every witness before testifying shall take an oath or make an
affirmation or declaration in the form provided by law, except that a
child under the age of 10 or a dependent person with a substantial
cognitive impairment, in the court's discretion, may be required only
to promise to tell the truth.

711.  At the trial of an action, a witness can be heard only in the
presence and subject to the examination of all the parties to the
action, if they choose to attend and examine.

712.  Notwithstanding Sections 711 and 1200, at the trial of a
criminal action, evidence of the technique used in taking blood
samples may be given by a registered nurse, licensed vocational
nurse, or licensed clinical laboratory technologist or clinical
laboratory bioanalyst, by means of an affidavit. The affidavit shall
be admissible, provided the party offering the affidavit as evidence
has served all other parties to the action, or their counsel, with a
copy of the affidavit no less than 10 days prior to trial. Nothing in
this section shall preclude any party or his counsel from objecting
to the introduction of the affidavit at any time, and requiring the
attendance of the affiant, or compelling attendance by subpoena.