In a large mixing bowl, toss together mixed berries (a combination of blueberries, raspberries, boysenberries, or blackberries) with lemon juice.
In a separate bowl, combine sugar, flour, tapioca, salt and cinnamon.
Prepare Papa's Pie crust according to directions. Place one pie shell into a 9-inch pie plate. Take a fork and pierce holes in the bottom of the crust.
Layer berries alternately with sugar mixture, until pie shell is filled.
Cover with top crust, cut away excess dough, seal and flute edges. Make several small slits in the top to allow steam to escape or make a lattice top.
Bake at 450 degrees for 10 minutes, then lower to 350 degrees and bake for 30 minutes longer.