The way it was explained to me... if its in your home, its considered in your possession . Even if your not home.
Unfortunately, that's not the way the BATFE sees it. If you're not the registered owner or your name isn't on the trust, you can't have possession of the NFA item.
Say you got a CLEO sign-off for the NFA item and you're the registered owner, or you purchased it through a trust but your wife isn't on it: If you're not home and your wife accesses the safe where the item is kept she's in violation of federal law and is eligible to receive ten years of prison food.