Muddle 2 cups blackberries with 2 cups simple syrup (recipe follows) in a pitcher. Stir in 2 cups each fresh lemon juice and water; add ice and lemon slices.
Simple Syrup: To make 2 cups simple syrup, bring 1 1/2cups each sugar and water to a boil, stirring until dissolved. Let cool.
Recipe shared from: http://www.foodnetwork.com/recipes/blackberry-lemonade-recipe/index.html