Rule 705: Disclosing the Facts or Data Underlying an Expert's Opinion

Rule 705 streamlines the presentation of expert testimony. Under the old common law, experts were often required to sit through lengthy hypothetical questions reciting all the facts they relied on before they could give their opinion. This was tedious, time-consuming, and often confusing for juries.

Under Rule 705, an expert can cut straight to the opinion without first laying out every underlying fact or piece of data. The expert can state the opinion and then explain the reasoning, or the proponent can elicit the bases on direct examination in whatever order makes the most sense. This gives the presenting attorney flexibility in how to structure the expert's testimony for maximum clarity and impact.

The safeguard is cross-examination. The opposing party has the right to probe the underlying facts and data on cross-examination, exposing any weaknesses in the expert's foundation. If the expert's opinion lacks an adequate basis, cross-examination will reveal this. The court also retains discretion to require disclosure of the underlying facts before the opinion is given if the circumstances warrant it.