In almost all respects, Illinois law disfavors offering the jury any external commentary on the credibility of witnesses. For example, a prosecutor commits error if he tells the jury that he found one of the witnesses particularly believable. Similarly, a defense attorney may not ask his witness to comment on the veracity of another witness. Nor may a nurse testify about whether she found a child’s allegations of sexual abuse credible. Rules such as these are intended to protect the jury’s role as sole …