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.
There’s a definite correlation between the size of personal injury verdicts and the effectiveness of testimony by medical experts. Well-prepared and well-presented medical testimony carries weight and convinces triers of fact. The recent $289 million verdict against Monsanto may be an example.
Retaining an expert witness is expensive and may not be necessary in every case. Don’t try to keep up with the Jones & Jones firm: Just because the other side has an expert or because experts have traditionally been used in similar cases doesn’t mean you need one. And if you decide you do need an expert, make sure it’s the best type for your case.
Despite the political rhetoric, public confidence in scientists has “remained stable for decades.” You can bring this confidence into the courtroom through expert testimony based on the scientific method, i.e., physical observation and testing, not just untested hypotheses. Experts should be “hands on” when it comes to collecting and investigating physical evidence.
As James Beck of Reed Smith puts it, “California has long gone its merry, idiosyncratic way in the Daubert/Frye wars.” That’s why it was a big surprise when the California Supreme Court cut off this legal tangent and stated that California courts must apply the same Daubert standard as their federal counterparts when it comes to admitting opinion testimony not based on a new scientific technique.