What do you do? Block the inquiry, or invite all available testing to prove your innocence?
Exactly.
Not only do you block the inquiry, you enlist the help of powerful people and the media to stall it even further, as it grows remoter and remoter in the minds of an easily distracted public, until the money for legal battles runs out, and everything is dropped or watered down to insignificance.
Having witnesses to parallels samples which are sent to an independent lab for verification just in case someone decides to cook the books.