There is no doubt that the trial court has the power to replace an original juror with an alternate upon finding that the juror is "unable to perform his duty." ( Pen. Code, 1089; see Code Civ. Proc., 233.) Penal Code section 1089 states in 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 duty, or if a juror requests a discharge and good cause appears therefor, the court may order him to be discharged and draw the name of an alternate, who shall then take his place in the jury box, and be subject to the same rules and regulations as though he had been selected as one of the original jurors." Code of Civil Procedure section 233 provides: "If, before the jury has returned its verdict to the court, a juror becomes sick 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. If any alternate jurors have been selected as provided by law, one of them shall then be designated by the court to take the place of the juror so discharged. If after all alternate jurors have been made regular jurors or if there is no alternate juror, a juror becomes sick or otherwise unable to perform the juror's duty and has been discharged by the court as provided in this section, the jury shall be discharged and a new jury then or afterwards impaneled, and the cause may again be tried. Alternatively, with the consent of all parties, the trial may proceed with only the remaining jurors, or another juror may be sworn and the trial begin anew." The latter statute is part of the Trial Jury Selection and Management Act ( Code Civ. Proc., 190 et. seq.), and as such "applies to the selection of jurors, and the formation of trial juries, for both civil and criminal cases, in all trial courts of the state." ( Code Civ. Proc., 192.) Courts have found sufficient cause to discharge and replace a juror who conceals or misstates facts in response to voir dire or other questioning, sleeps or otherwise fails to attend to the proceedings, betrays bias or a fixed prejudgment of the issues, exhibits an inability or refusal to deliberate, disclaims the ability or willingness to apply the law as given by the court, or fails to comply with other duties imposed on jurors. Good cause for substitution may also be found where a juror's emotional state threatens his or her ability to receive and consider the evidence or to deliberate.