California Code, Family Code - FAM § 3023

(a) If custody of a minor child is the sole contested issue, the case shall be given preference over other civil cases, except matters to which special precedence may be given by law, for assigning a trial date and shall be given an early hearing.

(b) If there is more than one contested issue and one of the issues is the custody of a minor child, the court, as to the issue of custody, shall order a separate trial.  The separate trial shall be given preference over other civil cases, except matters to which special precedence may be given by law, for assigning a trial date.