Section 24(1)(a) of the Mental Health Act 1990 (NSW) requires that the offence the person is believed to be committing or to have recently committed must be one that would enable the officer to arrest the person forthwith; an alleged offence committed four days earlier does not qualify as 'recently committed'. A police officer's genuine but erroneous belief in statutory authority to detain precludes aggravated damages but does not prevent an award of compensatory damages for false imprisonment. Where police unlawfully apprehend a person and take them to hospital, the period of imprisonment for damages purposes runs from apprehension until release from hospital.
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