Some will never admit to their crime until their last dying day in jail. One case I saw the other night the police released on the news that they knew where the body would be and were starting digging tomorrow and the suspect came out to spy on them. After he left the police went to his point of view and narrowed down where the body could be - in a vast area of fields. They went to that probable body area the next day and the suspect saw them and acted and went out that night to try and move the body. He showed them where it was. That was entrapment because they really had no idea where the body was. They lied and took a risk that the suspect would get scared about the news and act and it paid off.
So what do you think the reason was for the PJ to take the decision to lie to the McCanns about the 100%DNA match? What were they hoping to achieve by employing that tactic?
All it did achieve IMO was to alarm the parents into thinking the PJ may have evidence that Madeleine was dead and caused them great distress. IIRC they begged the PJ to tell them if that was the case - as up until that point they were hoping she would be found alive. (from memory so am not sure whether this applied to both parents or just to Gerry)
However, hardly the reaction one would expect from guilty people to the news that 100% DNA evidence had been found and who would then realise that their goose was well on the way to being cooked IMO.