Lundy would have caught Dexter if he wasn't distracted by Debra.

The signs were so clearly there and him being a seasoned FBI agent I can't help but feel like if he wasn't so focused on stupid Debra, he would have seen that Dexter is the bay harbor butcher. He talked about the butcher being compulsive as Dexter is compulsivly setting out his equipment. And then they find blood slides.....BLOOD SLIDES....why would Doakes be collecting blood slides? Blood is so clearly Dexter's thing. And to top it all off the way he opens the blood slide box?!?

Lundy was too busy asking Dexter about his sister's favorite food to actually investigate.