How far can police go in obtain­ing evi­dence with­out per­mis­sion? There are some instances (called “exi­gent cir­cum­stances”) in which the law holds that Fourth Amend­ment pro­tec­tion against unrea­son­able searches and seizures, and the need for a search war­rant, are com­monly sus­pended. The lim­its of this idea will be tested in the Supreme Court today.

The case of Mis­souri v. McNeely asks whether a law enforce­ment offi­cer may obtain a non­con­sen­sual and war­rant­less blood sam­ple from some­one sus­pected of dri­ving while intox­i­cated, under the argu­ment that wait­ing the time needed to obtain a war­rant would allow “the nat­ural dis­si­pa­tion of alco­hol in the blood­stream.” This, argues the State of Mis­souri, pro­vides “exi­gent cir­cum­stances” which per­mit the State to over­ride the driver’s Fourth Amend­ment rights.

On Octo­ber 3, 2010, Tyler McNeely was pulled over by Mis­souri state police offi­cer Mark Winder for dri­ving above the speed limit, and for three times drift­ing over the cen­ter­line. Offi­cer Winder claimed to observe that McNeely’s eyes were “red and glassy,” and that McNeely’s breath smelled of alco­hol. Offi­cer Winder sub­jected McNeely to a series of four field sobri­ety tests, on which McNeely per­formed poorly.

McNeely refused to sub­mit to a breath­a­lyzer test. Offi­cer Winder then arrested him for dri­ving while intox­i­cated and brought him to St. Fran­cis Med­ical Cen­ter in Cape Girardeau to obtain a blood sam­ple. McNeely refused to coöper­ate. Winder read him the Mis­souri “implied con­sent” law. Some­thing like the shrinkwrap “agree­ments” that come with soft­ware in which the seller imposes con­di­tions on the sale (and which buy­ers almost never read), “implied con­sent” laws hold that con­sent to var­i­ous con­di­tions is rea­son­ably inferred “from signs, actions, or facts, or by inac­tion or silence.” In this case, the fact that McNeely had a driver’s license is taken by the State as imply­ing he has con­sented to being sub­ject to such seizure of evi­dence as blood tests for alco­hol content.

This would have been McNeely’s third DWI offense. Poten­tially, he would be sub­ject to a four-​​year prison term. Even after being read the Mis­souri implied con­sent state­ment, McNeely still refused to will­ingly pro­vide a blood sam­ple. Offi­cer Winder ordered it to be taken any­way, and it was forcibly obtained. The test showed McNeely’s blood alco­hol level to be 0.154 per­cent, “well over” the legal limit. The State of Mis­souri sub­se­quently charged him with dri­ving while intox­i­cated. The case went to trial, and McNeely moved to have the blood test sup­pressed because it was obtained with­out a warrant.

In what may come as a sur­prise to many, the trial court agreed with McNeely. The State appealed this deci­sion, argu­ing, as described above, that the dan­ger of McNeely’s body metab­o­liz­ing the alco­hol out of his sys­tem rep­re­sented “exi­gent cir­cum­stances,” allow­ing them to forgo the time needed to obtain a war­rant. The appeals court held that the trial court had erred in its deci­sion, but that the case rep­re­sented a unique twist on nor­mal case law, and trans­ferred the whole thing to the Mis­souri Supreme Court.

Again, per­haps sur­pris­ingly, the Mis­souri high court ruled in McNeely’s favor. The State of Mis­souri appealed to the U.S. Supreme Court, and oral argu­ments in the case will be heard today.

This is a chance for the Supreme Court to resolve dif­fer­ent rul­ings among the sev­eral states:

The top courts in Wis­con­sin, Min­nesota, and Ore­gon have all ruled that the rapid dis­si­pa­tion of alco­hol in the blood­stream is a suf­fi­cient exi­gency to jus­tify a war­rant­less blood test.

In con­trast, state high courts in Iowa, Utah, and Mis­souri have ruled that dis­si­pa­tion does not excuse police from obtain­ing a war­rant before con­duct­ing an invol­un­tary blood test.

McNeely is being defended in the Supreme Court by the Amer­i­can Civil Lib­er­ties Union, which argues:

War­rant­less searches are pre­sump­tively unrea­son­able under the Fourth Amend­ment. Missouri’s argu­ment in favor of a cat­e­gor­i­cal excep­tion to the war­rant require­ment in all DWI cases was unan­i­mously rejected by the Mis­souri Supreme Court. Missouri’s claim that a cat­e­gor­i­cal excep­tion to the war­rant require­ment is nec­es­sary to ensure effec­tive enforce­ment of the DWI laws is con­tra­dicted by the expe­ri­ence of 26 states that pro­hibit war­rant­less blood draws in rou­tine DWI cases, like this one.

Note that the facts of this case are not in dis­pute. McNeely was dri­ving wile intox­i­cated, and the State wanted to set aside his Fourth Amend­ment rights in order to prove it. Note also that Mis­souri is appar­ently not argu­ing that the “pub­lic good” of pre­vent­ing some­one from dri­ving drunk is suf­fi­cient rea­son to over­ride the Fourth Amend­ment. The State is argu­ing instead that it’s a mat­ter of tim­ing.

What do you think about this case? More than half of the States agree with McNeely and the ACLU. Do you agree that a war­rant should be required to obtain blood from a sus­pect, even in the case of drunk dri­ving? Does the time needed to obtain a war­rant, as com­pared to the time for the evi­dence (in this case, the level of alco­hol in the blood) to dis­si­pate, pro­vide suf­fi­cient rea­son to set aside a Con­sti­tu­tional right?