Fair point. Perhaps a grandfather clause of sorts then to cover both instances?

Genuine Answer: While it may deter new instances, it comes at the cost of potentially harming the currently falsely accused by never letting them get justice because the fake accuser decides the cost is too high to come clean. The most precious thing we have is our time and freedom. What decision would you prefer if you were in the shoes of the falsely accused?

Its not ideal, but it is something that requires a little more consideration.