[1][3][4] From 1958 to 1961, he was also a candidate for succession and from 1961, succeeding the deceased Hans Loch, to 1990 a member of the Volkskammer,[1][2] nominally representing a constituency in southern Bezirk Potsdam.

[1][2][3][4] The head of the main department responsible for legislation during Heusinger's tenure was Justice Councilor Gustav-Adolf Lübchen.

[1][4] During the Wende, Heusinger was one of only a few Ministers kept by the new transitional government of Hans Modrow, though he did lose the deputy chairman title.

[8] The LDP, its new name after being renamed in February 1990, joined forces with the other liberal parties in the GDR to form the Association of Free Democrats (BFD).

[1][2][4] After German reunification, Heusinger became active in the Society for Legal and Humanitarian Assistance (German: Gesellschaft zur Rechtlichen und Humanitären Unterstützung) (GRH),[1][2] a historical negationist lobbying group for former GDR functionaries accused of political repression.