Chapter 1. Competency of California Evidence Code >> Division 6. >> Chapter 1.

Except as otherwise provided by statute, every person, irrespective of age, is qualified to be a witness and no person is disqualified to testify to any matter.

(a) A person is disqualified to be a witness if he or she is:
  (1) Incapable of expressing himself or herself concerning the matter so as to be understood, either directly or through interpretation by one who can understand him; or
  (2) Incapable of understanding the duty of a witness to tell the truth.
  (b) In any proceeding held outside the presence of a jury, the court may reserve challenges to the competency of a witness until the conclusion of the direct examination of that witness.

(a) Subject to Section 801, the testimony of a witness concerning a particular matter is inadmissible unless he has personal knowledge of the matter. Against the objection of a party, such personal knowledge must be shown before the witness may testify concerning the matter.
  (b) A witness' personal knowledge of a matter may be shown by any otherwise admissible evidence, including his own testimony.

(a) Before the judge presiding at the trial of an action may be called to testify in that trial as a witness, he shall, in proceedings held out of the presence and hearing of the jury, inform the parties of the information he has concerning any fact or matter about which he will be called to testify.
  (b) Against the objection of a party, the judge presiding at the trial of an action may not testify in that trial as a witness. Upon such objection, the judge shall declare a mistrial and order the action assigned for trial before another judge.
  (c) The calling of the judge presiding at a trial to testify in that trial as a witness shall be deemed a consent to the granting of a motion for mistrial, and an objection to such calling of a judge shall be deemed a motion for mistrial.
  (d) In the absence of objection by a party, the judge presiding at the trial of an action may testify in that trial as a witness.

No person presiding at any judicial or quasi-judicial proceeding, and no arbitrator or mediator, shall be competent to testify, in any subsequent civil proceeding, as to any statement, conduct, decision, or ruling, occurring at or in conjunction with the prior proceeding, except as to a statement or conduct that could (a) give rise to civil or criminal contempt, (b) constitute a crime, (c) be the subject of investigation by the State Bar or Commission on Judicial Performance, or (d) give rise to disqualification proceedings under paragraph (1) or (6) of subdivision (a) of Section 170.1 of the Code of Civil Procedure. However, this section does not apply to a mediator with regard to any mediation under Chapter 11 (commencing with Section 3160) of Part 2 of Division 8 of the Family Code.

(a) Before a juror sworn and impaneled in the trial of an action may be called to testify before the jury in that trial as a witness, he shall, in proceedings conducted by the court out of the presence and hearing of the remaining jurors, inform the parties of the information he has concerning any fact or matter about which he will be called to testify.
  (b) Against the objection of a party, a juror sworn and impaneled in the trial of an action may not testify before the jury in that trial as a witness. Upon such objection, the court shall declare a mistrial and order the action assigned for trial before another jury.
  (c) The calling of a juror to testify before the jury as a witness shall be deemed a consent to the granting of a motion for mistrial, and an objection to such calling of a juror shall be deemed a motion for mistrial.
  (d) In the absence of objection by a party, a juror sworn and impaneled in the trial of an action may be compelled to testify in that trial as a witness.