Special non est factum
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
A form of the plea of non est factum, in debt on a specialty, by which the defendant alleges that, although he executed the deed, yet it is in law "not his deed," because of certain special circumstances which he proceeds to set out; as, where he delivered the deed as an escrow, and it was turned over to the plaintiff prematurely or without performance of the condition.