18.2-22. Conspiracy to commit felony - Is possible however, a whole hell of a lot of this is going to depend on Barb consenting to a rape kit, If she won't consent then the county / state will have to petition the court to say she is mentally incapable and they have to make decisions for her (or a family member does but at this point who ?).
Then it comes to what evidence can they get that shows Chris did it - So virginia is a single party state for recorded phone calls, so those being admitted as evidence would depend on where the call originated from as to its admissibility.
Then we have Chris, any half ass attorney will argue he is not fit for interview or trial and the state will have to consider what are the chances of getting a prosecution, and I doubt they will go to bat on it unless the fucker is interviewed and admits it.
The fact he is not being held suggests there is a lack of evidence at this time.
I am only guessing but my gut tells me this wont go the distance on a rape charge and Barb will taken in by the state the house sold and Chris will continue to live a fucked up life.