Maxwell was convicted by a jury of her peers. Child abuse is so rampant (shown by her own network and length of time they were allowed to operate) that she will not find a jury, and cannot ask that every juror is cleared of having any background of sexual abuse. A jury if her peers means she takes the jury she finds in front of her. Had her lawyers done their job, this juror would have been exposed and would not have been chosen to sit, they are allowed to veto jurors.
The Court takes the jury after a lengthy process, that process was followed. Unless this juror actually lied and that is proven, then it is a failed of the Defence team not to weed out jurors with past abuse issues.