I think the biggest and most important question is.. What is, the evidence that the parents, are involved... This is what Netflix chose to investigate and answer.... And I think they did...
You only had to listen to what journalist Sandra Felgueiras had to say on the matter bearing in mind the way she went for the jugular in many interviews and articles.
She believed what her police sources were telling her at the time.
The knowledge that the police consistently lied to her and fed her lies about Kate and Gerry throughout the investigation.
She believed what she was told about the 'strange behaviour'.
She believed what she was told about 'CALPOL'.
She believed what she was told about the dog 'evidence'.
She could not emphasise enough in the Netflix film her embarrassment about the lies she had spread about Kate and Gerry as a direct result of lies the police had fed her.
She demanded answers from Amaral, long suspected of being her informant and therefore the source of the lies, when the truth became apparent.