Originally Posted by Odin88

Any constable or other person may without warrant apprehend:

a) any person in the act of, or immediately after having committed an offence punishable under any Act.

b) any person who has commited a serious indictable offence for which the person has not been tried.

And take that person, and any possessions found on that person, before an authorised justice to be dealt with according to the law.

Crimes Act 1900

Of course this only applies to NSW Australia :P