This 'informant' needs to end up in the witness stand, under oath, in a Civil Rights action.
In my experience, admittedly a long time ago, informants get an incredible amount of protection. It began when we swore out that affidavit in support of a warrant - search or arrest, it didn’t matter. We referred to the informant by the pronoun ‘it’, not ‘he’ or ‘she’. Things got more nebulous from there. Only once do I remember a judge demanding to interview the informant personally, and that was after the fact. It seems we were given some bum scoop and arrested the wrong man. His crime? He was family.