TRunk leak

Hello,

I have a 1998 Corolla with a deflector and I have a little problem with water leaking in the trunk door.

When you open the trunk after a rain, water comes out through the bottom of the door. At first I tought it might be comming from the deflector but I sealed it and it continues. I tried putting a silicon seal under the lights, but it didn't work. How can I know were the water comes from and how do I fix this.

Thanks

Thomas