When a motorist is arrest­ed on sus­pi­cion of intox­i­cat­ed dri­ving, the gov­ern­ment can­not com­pel him to sub­mit to a blood draw with­out a war­rant or war­rant excep­tion, nor can it make his refusal to sub­mit to a blood draw a crime. But can the gov­ern­ment use the refusal as evi­dence of guilt in a sub­se­quent DUI pros­e­cu­tion on the basis of an implied con­sent statute? In this Con­tri­bu­tion, Max Baum­bach (’21) argues that the Fourth Amend­ment pro­hibits the use of blood test refusal evi­dence in a DUI pros­e­cu­tion where the test itself would have been unlaw­ful to con­duct in the first instance.