Ruby Central isn't capable of giving clemency. They could refuse to testify in any prosecution, but they don't get to pick whether a relevant attorney general or district attorney decides to prosecute.
Legally, they can state a preference not to testify, but they couldn't (legally) refuse to if issued a subpoena. (And, even more emphatically, they couldn't accept a good or service from the person who might be charged in exchange for not reporting the crime, or for refusing testimony.)
