Rule 705 Disclosure of Facts or Data Underlying Expert Opinion

When an expert witness testifies in court, they don't have to explain all the facts and information behind their opinion before they share that opinion. They can simply state their conclusion and give their reasons, without walking through every piece of evidence first. A judge can change this and require the expert to explain their basis upfront, but that's not the usual practice.

However, the other side gets a chance to dig into this during cross-examination. Even if the expert didn't explain their reasoning at first, the opposing lawyer can ask questions to force the expert to reveal what facts or data they relied on. This gives both sides a fair chance: the expert can present their opinion efficiently, but their reasoning can still be tested and challenged later in the questioning.