demeanor or conduct of the party sought to be bound thereby. And, whether it is acquiescence in the conduct or in the language of others, it must plainly appear that such conduct was fully known or the language fully understood by such party before any inference can be drawn by his silence.’ [Citations omitted.] ... ‘The mere silence of one, when facts are asserted in his presence, is no ground of presuming his acquiescence unless the conversation was addressed to him under such circumstances as to call for a reply.’ ” (Emphasis added.) See also Palmer v. Fuqua, 641 F.2d 1146, 1160 (5th Cir.1981) (To prove the defense of estoppel by silence, it must be shown that the party who failed to speak had a duty to speak.); Champlin Oil & Ref. Co. v. Chastain, 403 S.W.2d 376, 404 (Tex.1965) (<HOLDING>); City of Mesquite v. Rawlins, 399 S.W.2d 162,
holding that upon choosing to speak one has a duty to be both accurate and complete  holding that silence can constitute misrepresentation when there is duty to speak holding that the government may comment on a defendants prearrest premiranda silence as well as his postarrest pr emiranda silence holding that a district attorneys duty to preserve exculpatory evidence would arise from his role as an officer of the court charged to do justice an act or an omission concerning such a duty cannot be construed as only administrative or investigative it too is necessarily related to the prosecutors preparation to prosecute holding that objection was called for by the party to be estopped since an  estoppel may arise as effectually from silence where it is a duty to speak as from words spoken 