The Ruby Princess cruise ship off the coast of Sydney (Image: AAP/Joel Carrett)

NSW Police Commissioner Mick Fuller has started a criminal investigation into the Ruby Princess scandal -- a scandal which, at last count, has led to the deaths of 11 passengers.

The commissioner said preliminary inquiries into phone call logs, email correspondence, radio transmissions and other documents had raised concerns about potentially misleading conduct.

Here's Inq's list of 10 questions the commissioner should ask.