First, we must ask him questions about the world series.
Then force him to watch episodes of Hogan's Hero's.
To lure him in to a false sense of trust, make small talk regarding how hot Hilda (Klink's secretary) was.
After studying his reactions to certain scenes, perform the following:
- If he laughs at the bumbling German characters, then have a holocaust survivor punch him in the gut (per willravel) and let him stay.
- If he acts indignant toward the ineptitude of Col. Klink and Sgt. Schultz, or if he cheers for SS Maj. Hochstetter, then give him "30 days in the cooler" and deport him.
Seriously, I'd let him stay until hard evidence is found that he performed any cruelties to the prisoners. If he is guilty, then send him back to Germany.