So I can imagine that the informant really played it up and made it all sound real good to the police.
Since he had provided good information in the past. his credit rating was good and they believed him.
The police can be told by a victim that they were assaulted and a warrant can be obtained with no evidence. This is how our system works. You submit a request and present the evidence you have. In the case of a victim.... his word alone.
So this is what the police did.... the obtained their paperwork on what they believed to be true from a credible informant.
It will be interesting to see what happens in court.