Police on the Madeleine McCann case initially believed her parents accidentally killed her with a Paracetamol overdose, according to a Netflix documentary.
The Netflix documentary The Disappearance of Madeleine McCann delves into how police turned their attention to Gerry and Kate McCann just months into the investigation.
Three-year-old Madeleine McCann vanished from the family's accommodation on May 3, 2007.
Authorities were particularly interested in a conversation between Kate's father Brian Healy and media following Maddie's disappearance.
During an interview, Healy hinted at Kate giving Maddie Paracetamol to help her sleep, alerting police to investigate the family.
"Kate may have used Calpol [to help her sleep], but it's just outrageous to think of anything else."
This led police to investigate the couple, asking them a series of questions with Kate unable to answer more than 40 of them.
The documentary claims Kate and Gerry took turns to check on their children at the apartment, but at around 10pm they discovered Maddie was gone.
Investigator and author Anthony Summers told the documentary producers: "By late summer there was an implication that they may have over-sedated her by administering a drug."
His co-author, Robbyn Swan, said: "Essentially the Portuguese cops' case against the McCanns involved the following: that she died by accident on May 3; that the supposed checks on the children had been concocted; that they had hidden their daughter's body... and that her body had subsequently been transported in the rental car they had rented some weeks later."
Despite police probing the couple, the theory of Calpol has been discredited while forensics confirmed there was no links between Maddie's DNA to the apartment or car.
Jim Gamble, a former top child protection officer, told producers: "Ultimately when you read through the detail of the DNA you see the absolute red herring it was, but it was a dangerous red herring because I think investigators in Portugal thought this was a smoking gun."
Portuguese journalist Sandra Felgueiras said she had felt "lied to" by her Portuguese police sources, who had tried to claim the evidence was damning.
She added: "When this happened I understood that the intention of those cops that were inside this investigation was not honest."
The confirmation enraged disgraced Portuguese office Goncalo Amaral who released a book called The Truth of the Lie, alleging the McCanns had faked Maddie's abduction after accidentally killing her.
He said "all they did at the time was lie" to police, accusing them of making up their movements on the night of Maddie's disappearance.
The McCanns launched legal action against Amaral in 2009 and were awarded £450,000 ($871,600) before the Portuguese officer won an appeal against the decision.