In People v. Williams (2001) 25 Cal.4th 441, the Court "re-affirmed. . . the basic rule that jurors are required to determine the facts and render a verdict in accordance with the court's instructions on the law. A juror who is unable or unwilling to do so is 'unable to perform his duty' as a juror ( 1089) and may be discharged." ( Id. at p. 463.) As the Court made clear: "The circumstance that, as a practical matter, the jury in a criminal case may have the ability to disregard the court's instructions in the defendant's favor without recourse by the prosecution does not diminish the trial court's authority to discharge a juror who, the court learns, is unable or unwilling to follow the court's instructions." ( Id. at p. 449.) The California high court explained, "A criminal defendant has a constitutional right to an impartial jury, and the pretrial voir dire process is important because it enables the trial court and the parties to determine whether a prospective juror is unbiased and both can and will follow the law. But the voir dire process works only if jurors answer questions truthfully." (People v. Wilson (2008) 44 Cal.4th 758, 822.) "'Although intentional concealment of material information by a potential juror may constitute implied bias justifying his or her disqualification or removal , mere inadvertent or unintentional failures to disclose are not accorded the same effect. "The proper test to be applied to unintentional 'concealment' is whether the juror is sufficiently biased to constitute good cause for the court to find under . . . section 1089 . . . that he is unable to perform his duty."' " (People v. Wilson, supra, 44 Cal.4th at p. 823.) Penal Code Section 1089 provides in pertinent part: "If at any time, whether before or after the final submission of the case to the jury, a juror dies or becomes ill, or upon other good cause shown to the court is found to be unable to perform his or her duty, . . . the court may order the juror to be discharged and draw the name of an alternate, who shall then take a place in the jury box, and be subject to the same rules and regulations as though the alternate juror had been selected as one of the original jurors." "'"Before an appellate court will find error in failing to excuse a seated juror, the juror's inability to perform a juror's functions must be shown by the record to be a 'demonstrable reality.' The court will not presume bias, and will uphold the trial court's exercise of discretion on whether a seated juror should be discharged for good cause under section 1089 if supported by substantial evidence."' " (People v. Martinez (2010) 47 Cal.4th 911, 943.)