What is the test for determining cause of cause in a civil case?

"A trial court's ruling on a challenge for cause is reviewed for abuse of discretion. [Citation.] We will uphold the court's decision ' " ' "if it is fairly supported by the record, accepting as binding the trial court's determination as to the prospective juror's true state of mind when the prospective juror has made statements that are conflicting or ambiguous." [Citations.]' " ' " (People v. Merriman (2014) 60 Cal.4th 1, 50.)

"During voir dire, jurors commonly supply conflicting or equivocal responses to questions directed at their potential bias or incapacity to serve. When such conflicting or equivocal answers are given, the trial court, through its observation of the juror's demeanor as well as through its evaluation of the juror's verbal responses, is best suited to reach a conclusion regarding the juror's actual state of mind." (People v. Jones (2012) 54 Cal.4th 1, 41.)

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" '[A]ppellate courts recognize that a trial judge who observes and speaks with a prospective juror and hears that person's responses (noting, among other things, the person's tone of voice, apparent level of confidence, and demeanor), gleans valuable information that simply does not appear on the record.' [Citation.]" (Ibid.; accord, People v. Clark (2011) 52 Cal.4th 856, 895 ["The trial court is in the best position to determine the potential juror's true state of mind because it has observed firsthand the prospective juror's demeanor and verbal responses."].)