Rule 602 Need for Personal Knowledge

Before someone can testify about something in court, they have to actually know about it firsthand. This means they saw it, heard it, or experienced it themselves. A witness can't just guess, repeat rumors, or share something they only heard secondhand.

To show a witness has this firsthand knowledge, there needs to be some proof of it. This proof can come from the witness's own statements, like "I was standing right there when it happened." But it doesn't have to come only from the witness. Other evidence can also show the witness was in a position to know what they're testifying about.

There is one exception to this rule. Expert witnesses, like doctors or engineers, are allowed to give opinions based on their training and expertise, even if they didn't personally witness the events in the case. This exception is covered separately under Rule 703.