I don't think you can go to jail for being suspected of hiring assassin's but they can sure as hell be investigated.
I think she'd only go to jail for defamation/perjury and negligence in this hypothetical universe since she has too much dirt to get investigated.
I think you lost my chain of logic there.
If Defamation carries a life sentence, then claiming the Clintons have a trail of dead bodies would give said claimant a life sentence.
If Truth was a perfect defense against defamation charges, there would have to be sufficient proof in the courts to establish that the Clintons have such a body trail.
If the Clintons had such a body trail (provable to the courts) they would already be in prison.
The Clintons are not in prison.
Conclusion: you would not be able to use "But it's true" as a defense if the Clintons charged you with defamation and you would receive life in prison.
In general, mucking around with defamation laws is really tricky because such laws can be so easily abused. I don't much care for the current system where defamation is nearly impossible to make stick because the laws effectively require reading the media mogul's mine (you have to basically prove what they were thinking, not just their actions) but my preferred recourse is more along the lines of "retractions and public apologies must be printed/posted/advertised just as prominently as the original claim."
Such a requirement satisfies a certain sense of justice in being balanced, does not destroy the publisher's entire life for making a mistake, and most importantly goes a long way to restoring the damages to the victim by helping repair their reputation.