I know a lad who was sent down for two years for chasing a burglar and giving him a hiding.
The chap in question, lives in West End now, woke and heard something downstairs.
We went down, disturbed two youths who legged it. He chased them, barefoot and in his boxers, caught one and punched their lights out and then waited for the OB.
The OB knicked the youth and then, the following morning, nicked the fella in question.
He was charged with and convicted of GBH.
He was told that as soon as he gave chase it changed from self defence.
This was circa 1990/91.