1. Stir together blackberries and sugar; let stand 1 hour.
2. Process blackberry mixture in a blender or food processor until smooth. Pour through a fine wire-mesh strainer into a bowl; press with back of a spoon to squeeze out juice, discarding solids.
3. Cook juice mixture and remaining ingredients in a Dutch oven over medium-low heat 12 minutes or until thick and bubbly. Cool. Cover and chill 8 hours.