The general rule is that you need an expert witness to testify when the subject is “sufficiently beyond common experience that the opinion of that expert would assist the trier of fact.” Evid C §801(a). When it comes to a person’s sanity, you don’t always need an expert.
As Joseph DeAngelo (the “East Area Rapist”) may soon find out, a divorced spouse can spill a lot of beans. He was separated from his wife for years, but she’s just made divorce official and that’s a boon for the prosecution in his upcoming trial. But is she still limited in what she can say?
As with all witnesses, you must be able to control an expert witness during cross-examination. But many experts with experience in testifying treat cross-examiners like presidential candidates deal with the press: they ignore the question asked and answer the question they prefer. Here’s how to keep experts under your control.