Raspberry Mousse Pie

Lightly coat a 9-inch square metal baking pan with cooking spray and line with parchment paper, leaving a 2-inch overhang on all sides. Arrange graham crackers in an even layer in pan, breaking them to fit as necessary. Place lemon juice in a small bowl and sprinkle with gelatin. Let sit until gelatin softens, about 3 minutes. In a blender, puree 2 cups of raspberries until smooth,scraping down bowl as needed. Pour through a fine-mesh sieve into a measuring cup, pressing on solids (you should have about 1 cup of puree); discard solids.