Instead of calling upon principles, often helpless when a singular situation occurs, let's think :
Ricardo Paiva was faced with a dilemma : on one side he had to answer as a police officer in defence of his boss who was sued for assuming conclusions his whole team agreed with ; on the other side, in the name of his special relationship with Mrs McCann, he would conceal a dream that revealed a certain state of mind the calling of the hair device man corroborated.
This is a real "case of conscience" and it is worthwhile, imo, to meditate about it. There's no simple answer.
oh I think it was more than just a choice between 'defending' his boss ( who's conclusion he agreed with ) and revealing something told to him 'confidentially' by Kate McCann
He is a police officer ... there
is no 'confidentiality' between him and the main protagonists in a criminal investigation
I would guess that the telephone conversation about Kate's 'dream' was logged in police files ( quite properly ) and that the subsequent actions related to it are all recorded there too
Indeed, Kate says, in her book, that Paiva, accompanied by Jose de Frieitas, came to see her the next day ( following her phone call to him the night before, and whilst Gerry was still in Washington ) to discuss the anticipated search