No need to get over-excited, just because you got things a bit wrong. The PJ weren't perfect, but there's no evidence that they allowed people to flick cigarette ash everywhere contaminating forensic samples. When they did arrive they immediately cleared all the unneccessary people out of the apartment too, which the GNR had failed to do.
What did I get wrong exactly? Apart from anecdotal evidence as reported to journalists what other evidence would you expect to discover pertaining to fag ash being flicked around the apartment? Is cigarette ash routinely collected for forensic examination at crime scenes?
ETA
apparently it is!
Crucial evidence which could nail Madeleine McCann's abductor was contaminated by ash from policemen's cigarettes.
The ash was discovered by Portuguese forensic experts among samples from the McCanns' apartment in Praia da Luz taken soon after Madeleine vanished.
Three Portuguese detectives were seen smoking as they walked in and out of the ground-floor apartment on May 4, the day after Madeleine disappeared.
They were seen by a witness laughing and joking among themselves.
And when a passer-by asked what was happening one replied: "A little girl has wandered off but don't worry, we think she'll turn up."
After the ash was discovered at a police lab in the Portuguese capital Lisbon, tests carried out on it showed it matched the brand of cigarettes smoked by policemen who had been at the apartment.