"Catholics must gladly acknowledge and esteem the truly christian endowments which derive from our common heritage and which are to be found among our separated brothers and sisters. It is right and salutary to recognize the riches of Christ and the virtuous deeds in the lives of others who bear witness to Christ, even at times to the shedding of their blood. For God is always wonderful and his works too deserve our wonder."
Unitatis redintegratio 1.4; Decrees, ed. Tanner, vol. 2, p. 912. Cf. "Indeed there is a true bond in the holy Spirit, since it is he who is also at work in these persons with his sanctifying power through gifts and graces, and he has strengthened some of them to the point of the shedding of their blood" (Lumen gentium 2.25; Decrees, ed. Tanner, vol. 2, p. 861). P.-Th. Camelot sees this as "progress . . . by relation to the theologians and the canonists who hesitated to give the title and the merit of martyr to heretics or schismatics" (Catholicisme: hier, aujourd'hui, demain, s.v. Martyr (vol. 8, col. 775)), referring to DTC 10, col. 233 (1928), where R. Hedde, speaking of the heretic who dies for  a point of doctrine held in common ("provided that he be habitually disposed to believe all that would be proposed to him by the legitimate authority"), invokes the "Benedictine" distinction between his status coram Deo and his status coram Ecclesia. Coram Deo he may well be a true martyr; coram Ecclesia (which has no access to the heart) he is not. Yet Hedde questions even this: once it is admitted that a heretic invincibiliter may be a martyr coram Deo, won't it be necessary to grant this same status to the heretic who dies "with the same sincerity in order to defend an erroneous assertion that he believes to belong to the Christian Credo" (in order, in other words, to defend  what, from the Catholic point of view, is heresy in fact)?