It is not structural error for a trial court to erroneously sustain a prosecutor’s objection to a single peremptory challenge by the defense under CCP 231.7.  Assuming error under CCP 231.7, the defendant must show the error affected his right to a fair trial and impartial jury. (People v. Black (2014) 58 Cal.4th 912, 920.)  A defendant’s right to a fair trial and impartial jury is only affected when “an incompetent juror, meaning a juror who should have been removed for cause, sits on the jury that decides the case.” (Ibid.) In this case with child abuse and domestic violence allegations, the prospective juror’s remarks that she “would try” to remain fair and impartial, but “it’s hard when you’ve worked with children that have been through” domestic violence, did not reflect actual bias amounting to grounds to remove her for cause.

The full opinion is available on the court’s website here: https://www4.courts.ca.gov/opinions/documents/B330660.PDF