Larry, who is not a customer, arrives with Joe Customer. Larry hands Joe $20,000 and Joe Customer deposits the cash into his account. Is Larry a conductor? (having a debate over here)

I would include Larry in the CTR because he originally had the funds that were deposited into Joe's account

We were thinking If Larry is buying Joe's truck and Joe says 'meet me at the bank' because cash is involved - is Larry really a conductor? He conducted no transaction with the bank.

Or....Larry could be using his friend's account to do something nefarious. You didn't say what happened to the $20K after it was deposited, but that could weigh into my decision as to whether it's 'sold my car, meet me at the bank' or something worse.

Maybe you have a CTR and a SAR.

Ask the customer

I agree. There is no way to determine anything after the fact. Either the question as to what was happening was asked at the time of the transaction and information from the individuals was gathered at that time, as deemed necessary, or this is an exercise in futility.

Thanks for all the comments.