422. Pretending to be public officer or juror
A person who pretends to be or acts as a public officer or juror, when he or she is not lawfully authorised to act as such officer or juror, is liable on conviction on indictment to imprisonment for 5 years, unless he or she shows either—
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(a) that he or she pretended to be or acted as such officer or juror under a mistake of law or of fact;
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(b) in the case of a person acting as a public officer, that he or she so acted in good faith for the public benefit.