In Schmerber v. California, the Supreme Court ruled that, because the defendant was involved in a car crash and had to be taken to the hospital, the DUI chemical test without a warrant was reasonable. In Missouri v. McNeely, the Court ruled dissipation of alcohol in the blood, in and of itself, is not an exigent circumstance excusing the lack of a warrant.
In Mitchell v. Wisconsin, new to 2019, the Court ruled that someone who drinks to the level of unconsciousness and is arrested for DUI can be subjected to a blood test due to “unconsciousness” being widely considered a “medical emergency.” The court envisioned a situation where an unconscious driver causes a collision and has to go to the hospital, making it impractical to obtain a warrant.
I can see why some people would think this case effectively changed the DUI landscape, except the analysis is essentially the same as Schmerber. McNeely didn’t specifically say metabolizing blood alcohol is never an exigency, or that exigent circumstances cannot apply to DUI; it only said the body’s metabolism, in and of itself, is not an exigency. Schmerber dealt with the “perfect storm” where the defendant needs medical treatment because of a collision. Mitchell didn’t change that; it just added another scenario.
Having an attorney that can recognize these differences in the new laws is incredibly important in successfully defending against DUI cases.