Is it mistake of law or fact? Why?

Question

Plaintiff was intentionally misinformed during hospitalization that attending doctor did not lead discharge arrangements.  
 
Discharge arrangements led to damages. During legal case plaintiff decided to dismiss case against doctor without propounding discovery on defendant doctor. Plaintiff later discovered that doctor led discharge arrangements and made record of terminal disease knowingly that it was non-existent. 
Is it mistake of law or fact? 
Why?

James L. Arrasmith · Answer

This situation involves a mistake of fact, not a mistake of law. The key distinction lies in what the plaintiff was unaware of - specifically, the doctor's direct involvement in discharge arrangements and false medical records. 
 
The error centers around factual circumstances that were concealed or misrepresented, including who made the discharge decisions and the accuracy of medical documentation. These are concrete, verifiable elements of reality that were unknown to the plaintiff when making the decision to dismiss the case. This differs from a mistake of law, which would involve misunderstanding legal rights, procedures, or consequences. 
 
If you had proceeded with discovery before dismissal, these facts likely would have come to light, potentially changing your legal strategy. Under California law, this type of factual mistake could potentially support a motion to set aside the dismissal, particularly since the concealment appears intentional. You might want to consult with a legal professional about your options for reopening the case based on these newly discovered facts, as courts generally view intentional concealment of material facts more seriously than innocent mistakes.

Q: Is it mistake of law or fact? Why?