Rule 701 (a) A person is disqualified to be a witness if he or she is: (1) Incapable of expressing himself or herself concerning the matter so as to be underst…

Not everyone can automatically testify in a California court case. To be a witness, a person must be able to communicate clearly enough to be understood, either on their own or through an interpreter. They also must understand that witnesses are required to tell the truth.

If someone cannot meet these two basic requirements, the court will not allow them to testify. This could apply to very young children, people with certain disabilities, or anyone else who cannot communicate or grasp the meaning of telling the truth under oath.

When there is no jury present, a judge can wait until after a witness finishes their initial testimony before deciding whether that person was qualified to testify in the first place. This gives the judge a chance to see how the witness actually performs before making that call.