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Thoughts on United States v. Grubbs

As I mentioned earlier today, the Supreme Court has handed down the Grubbs case on the legality of anticipatory warrants. The end result: Anticipatory warrants are constitutional, within limits, and Judge Reinhardt’s special restrictions on their use have been eliminated. My overall assessment: The majority opinion does less damage than it might have, although I think Justice Scalia makes a mathematical error that might inadvertently alter the probable cause requirement.

I’ve written a lot on anticipatory warrants over at the Volokh Conspiracy and the NYU Journal of Law & Liberty, and the concern I have expressed is a simple one: The Fourth Amendment requires that probable cause must exist when the warrant is issued, not when the warrant is executed. Depending on how such warrants are limited, anticipatory warrants can be warrants that are issued before probable cause exists. I’ll assume the reader is familiar with these concerns; to get up to speed, see here, here, and here.

I thought Justice Scalia’s opinion did a reasonably good job addressing this concern. Here is the key passage:

It should be noted . . . that where the anticipatory warrant places a condition (other than the mere passage of time) upon its execution, the first of these determinations goes not merely to what will probably be found if the condition is met. (If that were the extent of the probability determination, an anticipatory warrant could be issued for every house in the country, authorizing search and seizure if contraband should be delivered—though for any single location there is no likelihood that contraband will be delivered.) Rather, the probability determination for a conditioned anticipatory warrant looks also to the likelihood that the condition will occur, and thus that a proper object of seizure will be on the described premises. In other words, for a conditioned anticipatory warrant to comply with the Fourth Amendment’s requirement of probable cause, two prerequisites of probability must be satisfied. It must be true not only that if the triggering condition occurs “there is a fair probability that contraband or evidence of a crime will be found in a particular place,” Gates, supra, at 238, but also that there is probable cause to believe the triggering condition will occur. The supporting affidavit must provide the magistrate with sufficient information to evaluate both aspects of the probable-cause determination.

I think Scalia is misstating probabilities a bit, as I’ll explain in a minute. My guess is that he means to say that the likelihood that the triggering condition must occur must be high enough that there is probable cause to believe that evidence will be found at the place to be searched. (That’s what he says at the beginning of the quoted paragraph.) As a result, probable cause is satisfied. If that’s what he has in mind, that’s a fair response to the concerns I have. It’s not a perfect answer, I think, as it seems to leave open the period of time before the triggering condition will occur. Give an officer enough time to wait until the triggering event occurs, and lots of triggering events will occur eventually (even if months or years down the road). Still, I imagine that the 10-day limit on when issued search warrants must be executed still applies, so the probable cause must be that the triggering event will occur in the 10-day window. In that case, an anticipatory warrant can only be issued if there is probable cause to believe that at some point in the 10-day window the evidence will be located there. If that’s right, I don’t think this opinion is inconsistent with the probable cause requirement (sorry, Mike).

Now, I said before that I think Scalia is misstating his probabilities a bit. Here’s the problem. The combination of 1) probable cause to believe that evidence will be present if a triggering event occurs, plus 2) probable cause to believe the triggering event will occur, does not equal 3) probable cause to believe that the evidence will be present. (Incidentally, “probable cause” and “fair probability” are the same under Gates.) If there is a 50% chance that evidence will be present if a package is delivered, and there is a 50% chance the package will be delivered, that doesn’t mean that there must be a 50% chance the evidence will be present.

If I’m not mistaken, the chances that the evidence will be present equals

(the chances the package will be delivered) X (the chances evidence will be present if the package is delivered) PLUS (the chances that the package won’t be delivered) X (the chances evidence will be present if the package isn’t delivered).

So if the likelihood that evidence will be present is 40% with the triggering event and 5% without it, and there is a 40% chance the triggering event will occur, then the likelihood when the warrant is issued that the evidence will be located at the place to be searched at some point in the 10-day window is actually 19%, not 40%.

I have a few additional thoughts about some rather strange dicta in the case, but I’ll probably save them for another post.