Combine cracker crumbs and butter; press onto the bottom of a greased 9-in. springform pan. Bake at 375° for 8-10 minutes or until lightly browned. Cool on a wire rack.
For filling, in a small saucepan, sprinkle gelatin over cold water; let stand for 1 minute. Heat over low heat, stirring until gelatin is completely dissolved. Add the semisweet chocolate; stir until melted.
In a large bowl, beat the cream cheese, sugar substitute and sugar until smooth. Gradually add the chocolate mixture and cocoa. Beat in vanilla. Pour onto crust; refrigerate for 2-3 hours or until firm.
Arrange raspberries on top of cheesecake. Carefully run a knife around edge of pan to loosen.
Editor's Note: This recipe was tested with Splenda no-calorie sweetener.