Although unfortunately the courts might rule that contraband found even in a voluntary search done by civilian personnel would be admissible in court, I beg to disagree.

A search at the airport is a search done by non-law enforcement civilians only for the purpose of checking for weapons or other direct threats to aviation security. I feel that any expansion on this search to include illegal items such as drugs and excessive 'cash' should be banned. If a security screener finds drugs, $50K, a human head, or whatever, their only course of action is to determine if the article is a threat to aviation security. Period. If not, then the passenger should be allowed to leave the checkpoint with whatever they have in their bag, and the screener needs to keep it to themselves, regardless of their personal beliefs, opinions, or self-delusions of being a cop.

If a cop is standing nearby, and happens to see the contraband in someone's bag (using the clearly defined rule of 'plain sight'), then the cop can take whatever action they feel is required at that point...NOT because a screener yelped "hey come look at this!".