Rule 703 Bases of Opinion Testimony by Experts

Expert witnesses can base their opinions on facts or information they learned before or during the trial. This includes things they saw themselves, or information other people gave them about the case.

The expert's opinion can rely on this information even if that information would not normally be allowed as evidence in court. The key requirement is that other experts in the same field would normally use this same type of information when forming their own opinions. So if doctors typically rely on certain kinds of reports or tests to reach conclusions, a medical expert in court can rely on those same kinds of reports or tests, even if the reports themselves could not be shown to the jury directly.

This rule exists because experts often need to consider a wide range of information to form a solid opinion, more than what strict evidence rules would normally permit. As long as the information is the type experts in that field would reasonably trust and use, it can support their testimony in court.