Work-product doctrine: In American civil procedure, the work-product doctrine protects materials prepared in anticipation of litigation from discovery by opposing counsel. It is also known as the work-product rule, the work-product immunity, the work-product privilege (somewhat erroneous terminology), and the work-product exception.
As it is clear from the above definition, the term has a number of variations. I suggest the best fitting variation which would deliver a suitable Arabic translation is the work-product privilege.
Good luck.