Legal basis: Paragraph 1 of Article 67 of the "Interpretation on the Application of the Criminal Procedure Law of the People's Republic of China" clearly stipulates the scope of witnesses. Specifically, the following people should not be witnesses in criminal proceedings:
1. People who are mentally or physically disabled or young and do not have the ability to discern or express correctly.
2. A person who has an interest in the case and may affect the fair handling of the case.