Section 32 of Evidence Act, provides as follows:
"32. Case in which statement of relevant fact by person who is dead or cannot be found, etc. is relevant - Statements, written or verbal, of relevant facts made by a person who is dead [...], are themselves relevant facts in the following cases -
(2) [...] made in course of business - When the statement was made by such person in the ordinary course of business, and in particular when it consists of any entry or memorandum made by him in books kept in the ordinary course of business, or in the discharge of professional duty; [...]."
On perusal of above provision, it would be clear that letter written Govt. Pleader may be considered evidence within the meaning of section 32 provided-
1) Letter must contain statement if deceased Govt. Pleader pertaining to relevant fact; and
2) It must have been issued in the ordinary course of business or in discharge of his professional duty.