As a 23-year police supervisor, I have difficulty believing someone under direct scrutiny by another police officer could survive questioning if they were not authentic. There are simply too many nuances of behavior and knowledge among the profession that only a police officer would know in depth. Superficially, perhaps they would pass scurtiny, but even as a local cop I know where the SS academy is, who the director is, what "G" grade a given level of agent is... all this stuff.

Police officers (and I count the SS as such) are very comfortable talking to each other and will quickly detect an anomaly.

While it is possible someone might go through an incredible amount of training to do this (as in the Soviet "Charm School,"), it would be much easier to just get a job as an airline catering employee with fake ID (as we saw happen in SLC).