Bit of a sidetrack, but I've noticed that it's a phrase used by people in our Melbourne office.
As a West Aussie, I've never heard any other Sandgropers use it.
Maybe it's a Victorian thing?

(And as I wrote that, I realised "Sandgropers" for West Australians seems to have faded out of usage)

NSW Police seem really quick at arresting famous sports players....

but mentally deranged psychos walking the street seem to be less of a priority.