Polygraph -  Refusal of :-
The use of the polygraph would play a vital role in the gathering of supportive evidence, in order to build an "Investigative Foundation" in such high profile cases.                                

This would also aid an investigation, where it would be prudent to establish departmental credibility at a later date, that may affect the trial and also when there is the lack of key evidence that should have been in place as applied in, (Crown - v - B J Murdoch)

To Establish, Perpetrator or Victim in-put without exclusion and, with all impartiallity. 

On using, test-string key-questions relating to Identity of the individual sitting the test and the specific case itself.

More so in the cases of missing persons where there may have been a second or third party within the crime scene, and or search footprint.

Would, "The Secondary Victim" take a test to exclude them from the investigation and, if not why not ?.

The priority must be, first and foremost in the best intrest of finding the Key victim,

In this case, "Maddie" Herself.

Credibility needs to be established in all high profile cases from day one in order to prevent. "Cold Case".

While the results of a polygraph test would not be admissable in a court of law as evidence, (Because such test are not considered to be conclusive)
it may still play a vital role in the foundation of Such cases.

The case of, Maddie McCann and, The case of, Peter Falconio.
Relative Key Questions are likely to present 75 percent, similar results.

Missing Persons Protocol, Cross Referenced Article.