A judge cannot be a witness in his own case.

Explanation

One who sits in judgment may not also testify as a fact witness — the dual role destroys the safeguard of impartiality.

Where this applies

• The judge wants to testify about what they personally witnessed in a case they're presiding over.
• A judge claims to have seen the defendant commit the crime — can they also judge the case?

See also

• 8.1.1 No man ought to be a judge in his own cause.