The "right to the funds" question is still to be resolved -- the Fed proposed bringing RDC and mRDC images under Reg CC and setting up an indemnity in favor of a bank that takes the physical check for deposit if the check is charged back, but the Fed's been ridiculously slow in finalizing its proposal, which is almost 3 years old now.
For now, the "rule" -- it's really a consensus -- is that whichever depositary bank gets the RDC/mRDC image (or the check-image from a physical deposit of the check) to the paying bank first should be the winner. But in practice, a paying bank confronted with having paid the "check" twice will take the easiest path to recovering its loss. If the Fed handled the items, the paying bank can send back either item using the PAID adjustment entry, and that determines which depositary bank loses.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8