He was supplied information from the forensic services.
Has Amaral claimed to be an expert in forensics ?
The other comments you make about 'sheer arrogance and incomptence' amount to no more than your biased opinion.
He was supplied with information from the experts which he was told proved nothing ... yet making the McCanns official suspects was the response.
Nothing at all to do with my opinion biased or otherwise ... quite simply stating the facts.
Quote
British scientists warned DNA tests on a sample from Kate and Gerry McCanns' hire car were inconclusive just days before they were made suspects, police files have revealed.
Forensic experts described how it was impossible to conclude whether swabbed bodily fluid taken from the vehicle's boot came from the couple's missing daughter Madeleine.
Despite the results from the Forensic Science Service (FSS), Portuguese detectives went on to name the McCanns "arguidos", or formal suspects in the case just four days later.
Significantly, officials even chose to cite DNA evidence as grounds for their suspicions.
https://www.theguardian.com/uk/2008/aug/04/madeleinemccann.portugal