Combine blackberries, liqueur, sugar, and juice in a medium saucepan over medium heat. Cook 8 minutes or until berries begin to soften; stir frequently.
Combine water and cornstarch in a small bowl, stirring with a whisk; stir into berry mixture. Bring to a boil; cook 1 minute or until thick, stirring constantly. Cool; pour into an airtight container. Cover and chill.
Note: Refrigerate jam in an airtight container for up to two weeks.