Well in the case of lead wouldn't the prediction be: a jurisdiction that removes lead from its petroleum products will experience a significant decrease in crime rates about 20 years later?
Here's why a testable, falsifiable theory is required for science. Let's say I'm a doctor and I've created a revolutionary cure for the common cold. My cure is to shake a dried gourd over the cold sufferer until he gets better. The cure might take a week, but it always works. My method is repeatable and perfectly reliable, and I've published my cure in a refereed scientific journal (there are now any number of phony refereed scientific journals). And, because (in this thought experiment) science can get along without defining, falsifiable theories, I'm under no obligation to try to explain my cure, or consider alternative explanations for my breakthrough — I only have to describe it, just as the linked article describes the correlation between lead in gasoline and the crime rate.
Because I've cured the common cold, and because I've met all the requirements that social psychology recognizes for science, I deserve a Nobel Prize. Yes or no?