Rule 11-602 Need for personal knowledge.

Before someone can testify about something, there has to be proof that they actually saw it, heard it, or otherwise experienced it firsthand. In other words, witnesses can only talk about things they truly know about from their own experience, not things they heard secondhand or assumed to be true.

The witness can prove they have this firsthand knowledge just by saying so in their testimony. For example, a witness can simply state that they were standing at the scene and saw what happened. That statement alone can be enough to show they have personal knowledge, as long as it's believable enough for a jury to accept it.

This rule does not apply to expert witnesses. Experts are allowed to give opinions based on their training, experience, or specialized knowledge, even if they did not personally witness the events in the case.