My trumped-up charge sheet was part of a PIP. The manager writes down a list of lies, and the HR person sits there and supports them. You are permitted to write a response, but it has no effect. You are warned that you may be fired at any time.
In this situation, you can't win. You can hire a lawyer -- but SAS can hire more lawyers. Your only good move is to leave.
This happened to me many years ago. At that time, SAS was still growing. So I was able to find another manager who wanted me, and move within the company.
It happened to two of my friends more recently. The company is no longer growing, so they had to leave SAS -- and compete against all the people laid off from other tech companies.
Ignorant people make jokes about trumped-up charge sheets. But in this economy, it's no joke if it happens to you.