Rule 602 Need for Personal Knowledge

When someone testifies in court, they can only speak about things they personally know. This means they must have seen, heard, or experienced something directly before they can talk about it in court. A witness cannot just repeat what someone else told them and present it as their own knowledge.

A witness can prove they have personal knowledge simply by saying so in their own testimony. For example, a witness can say "I saw this happen" or "I was there when it occurred." The exception to this rule is expert witnesses, who are allowed to base their opinions on outside information rather than things they personally experienced.