Whether a sanction will deter criminal behavior is a function of three elements: certainty, severity and celerity. Modern punishment policy has disproportionately focused on ratcheting up sanction severity in order to induce deterrence. Policymakers now increasingly look to policies that increase the certainty and celerity of punishment as an alternative to the high costs of more severe sanctions. South Dakota's 24/7 Sobriety Program is a novel, large-scale intervention requiring those arrested for or convicted of an alcohol-related offense to be tested for alcohol abstention compliance multiple times daily. Failing or missing a test results in a swift, certain, and moderate sanction. To estimate the causal effect of 24/7 on the probability of rearrest or probation revocation, we instrument for individual participation using program availability in the county of arrest. Results show that the probability of rearrest or probation revocation is 49 percent lower (p=0.002) for 24/7 participants than non-participants 12 months after their initial DUI arrest, and we detect substantive effects at 24 and 36 months, though the precision depends on the model specification. These findings provide evidence that it is possible to create a credible and effective deterrent threat on a large scale by prioritizing sanction certainty and celerity.