If officers wish to take a blood sample for a DUI, what must they do?

In situations where officers wish to take a blood sample for a DUI investigation, they generally must obtain a warrant if practical. This requirement stems from the Fourth Amendment, which protects individuals from unreasonable searches and seizures. The U.S. Supreme Court has established that, in most circumstances, a warrant is needed to conduct a blood draw unless specific exigent circumstances exist that would justify a warrantless search.

The rationale behind requiring a warrant is to ensure that the individual's privacy rights are respected. A blood draw is considered a more invasive procedure than breath tests, and therefore, the law typically requires law enforcement to have judicial approval before proceeding. Officers can act without a warrant in urgent situations where evidence might be lost (for example, if a person's blood alcohol content is quickly dissipating), but the general rule favors obtaining a warrant when it is practical to do so.

This principle is rooted in maintaining a balance between effective law enforcement and protecting constitutional rights. Thus, the optimal and legally sound approach when feasible is to acquire a warrant prior to taking a blood sample.