Drain raspberries, reserving juice. Add enough water to juice to measure two third cup. In saucepan, combine sugar and gelatin; add reserved liquid. Heat and stir until gelatin and sugar dissolve. Remove from heat. Gradually stir in yogurt and sour cream; mix well. Stir in raspberries. Pour into crust. chill until set, about 4 hours. Garnish with whipped topping as desired.