In Los Angeles, California, the victim of a robbery identifies his attacker as being one of three identical triplets (and the victim saw nobody but the one attacker). If the three triplets all live in separate homes, can the police get a search warrant for any of their homes (assuming no other evidence/motive)?

I would say each has 33% probability of being guilty, so my interpretation is that there is not "probable cause" (i.e., 50%) to search anyone's home...really?


A couple of SCOTUS decisions bearing on this are Texas v. Brown, 460 U.S. 730 and Illinois v. Gates, 462 U.S. 213, where the courts took pains to deny that "probable cause" is related to a number. From Texas v. Brown,

the Court frequently has remarked, probable cause is a flexible, common-sense standard. It merely required that the facts available to the officer would "warrant a man of reasonable caution in the belief," Carroll v. United States, 267 U. S. 132, 267 U. S. 162 (1925), that certain items may be contraband or stolen property or useful as evidence of a crime; it does not demand any showing that such a belief be correct, or more likely true than false. A "practical, nontechnical" probability that incriminating evidence is involved is all that is required. Brinegar v. United States, 338 U. S. 160

From Illinois v. Gates,

The task of the issuing magistrate is simply to make a practical, common sense decision whether, given all the circumstances set forth in the affidavit before him, there is a fair probability that contraband or evidence of a crime will be found in a particular place. And the duty of a reviewing court is simply to ensure that the magistrate had a substantial basis for concluding that probable cause existed.

The question is framed in terms of probability that a certain individual is guilty, but that is not the basis for issuing a search warrant. Rather, a warrant may be issued if there is a fair probability that evidence bearing on a crime will be found. That would include evidence that exonerates a person (the system is not set up to only favor convictions). It would be highly impractical to assign a numeric value to probability of finding evidence, since there is more to the matter than just declaring "It must have been one of these three people".

  • So, I gave all the details. Yes or no? – bobuhito May 14 at 5:11
  • If there is a very high probability that one of them is the thief, then there is also a high probability that three searches will find two innocent and one more likely guilty. There might be a problem if the police got three search warrants, and the first one finds everything that was stolen. So there is no reason to search the other two homes. – gnasher729 May 14 at 7:04
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    In practice, I have no doubt that a judge would find probable cause in the case in the OP. Whatever probability is necessary for probable cause, it is a weaker standard than a preponderance of the evidence (i.e. more likely than not). – ohwilleke May 14 at 20:36
  • @ohwilleke It's helpful to hear your opinion because I really thought "probable cause" meant roughly 50%, but now I will consider it to mean roughly 10%. I know it's hard to put numbers to this, but I believe the government has a duty to make this clearer...in case there is some such written guideline already given by the government, I hope someone could answer with a reference here. – bobuhito May 16 at 1:33
  • @bobuhito The case law makes a point of not quantifying probable cause numerically. There are lots and lots and lots of precedent making cases ruling regarding when fact patterns that do and do not establish probable cause. Even the SCOTUS case law alone would run to dozens of very specific cases. – ohwilleke May 17 at 22:06

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