[Quilla]

Which is one of the reasons why speculation she may be alive somewhere off the island is advantageous to the three young men being held.

Oh my, that may have been the motivation behind the Aruban suggesting Natalee's parents take a polygraph. This sounds more like an island-wide conspiracy every day.

[Rippersnapper]

Even disregarding the polygraph, just by having the locals suggest she is alive would create doubt that she is dead. They may have deliberately floated the idea, so the guys could go free.