As a court clerk, I am well-versed in the jury-selection process. First a computer randomly selects a few hundred citizens from the entire county to report for jury duty on a particular day. Then another computer assigns 40 of those present to a courtroom. Then the 40 names are placed in a drum, and a dozen names are pulled.
During jury selection for one trial, the judge asked potential Juror No. 12 if there was any reason he could not be a fair and impartial juror.

"There may be," he replied. "Juror No. 1 is my ex-wife, and if we were on the same jury, I guarantee we would not be able to agree on anything."

Both were excused.