Well, the police can also temper with any other evidence all the time anyway.
So it is anyway about trust - and how to check reliable, if they deserve trust.
This is how I would choose, which places to visit.
Australia is still quite good on that list, as cases where the police officers for example - are the ones doing the kidnapping and ransoming and investigation about it all by themself, like it is common in other places - are still quite rare.
My experience with australian police officers are a friendly warning for me, for ignoring a red light while at foot. And a asshole police officer stopping and handing out a hefty fine for us, for not "deadstopping" at a stop sign at a empty roadcrossing at night - explicitely, because we were driving a backpackers car and not a local one (he said so)
So all in all, I would probably visit again.