Rule 703 Bases of an Expert’s Opinion Testimony

When an expert witness gives their opinion in court, they can base that opinion on facts or information they learned about the case, whether they saw it themselves or someone told them about it. The information doesn't have to be the kind of evidence that would normally be allowed in court, as long as other experts in that same field would normally rely on that type of information to form their own opinions.

However, there's a limit on what the jury gets to hear. If the underlying facts or data wouldn't normally be allowed as evidence, the lawyer presenting the expert can only tell the jury about those facts if doing so helps the jury much more than it could hurt the other side. In other words, the judge has to be convinced that letting the jury hear this background information is mostly helpful for understanding the expert's opinion, not just something that might unfairly sway them against the other party.

This rule matters because expert witnesses often rely on reports, tests, or information from other people, not just things they personally witnessed. The rule lets experts use that kind of background information to form their opinions, while still giving the judge control over exactly what details the jury actually gets to hear.