Combine sugar, flour, and spices in a large bowl; gently stir in blackberries. Spoon into a 13x9 pan that has been sprayed with non-stick spray. Sprinkle with orange juice and set aside.

Re-roll the pie crust into a rectangle (if you prefer, you can use your favorite homemade crust recipe instead). Cut into 1-inch strips and arrange in a criss-cross pattern over the blackberry mixture.

Brush crust with milk, then sprinkle with sugar. Bake at 425 degrees for 35 minutes or until pastry is golden. Serve warm with ice cream or whipped cream.

Note: I've made this with 1/2 blackberries and 1/2 blueberries and it turned out great. Also, if you prefer to have a bottom crust as well, just double the pie crust - place one in the bottom of the sprayed pan; cover with berry mixture and juice; then finish with lattice.