Bake and cool pastry shell.
In heavy saucepan, cook raspberries in water for 5 minutes. Strain, retaining liquid. Add sugar and and cornstarch to liquid and cook until clear, stirring often.
Soften gelatin in water and add to mixture. Cool and add remaining berries and lemon juice. Pour into baked pie shell and chill.
Top with whipped cream and extra berries.