Unfortunately, this happens all of the time and the consequences have an effect upon the people who are falsely accused, the justice system, law enforcement, social services, and actual victims.
Has this matter gone to trial, yet? If not, you have the option of contacting the prosecuting and defending attorneys - he will be provided a public defense attorney. You will have the option of providing testimony on the falsely accused's behalf, and I would strongly encourage you to make that choice because, as I typed, this type of false accusation creates a cesspool for the real victims.