It depends. Do you mean biased as in a quick inference? Because if so then it could be biased because hes probably just checking out the people around the 'family'. Some families look different even when related, and sometimes you cant tell if they really are. So most of the survey would be biased if he doesnt directly ask them.
The movie isn't exactly like the myth. In myth, Perseus uses his magical sword to slay the sea beast. This is also the same sword he had used to slay Medusa.
