Take 1/3 of the berry mixture and place it in a small saucepan with the sugar, cornstarch, nutmeg, and salt.
Simmer 5-7 minutes, mashing periodically. Blend until smooth in a blender or with an immersion blender, if desired. The mixture should be thick like jelly.
Add the lemon juice to the berry puree.
Pour the berry puree into the graham cracker crust.
Toss the remaining berries with the melted preserves.
Gently spoon the remaining berries evenly on top of the puree.
Cover lightly and refrigerate at least 3 hours, up to 12.