I am undoubtedly remiss in having omitted from my earlier post the reigning definition of probable cause.  It was set forth in Illinois v. Gates, 462 U.S. 213 (1983), in the quotation that follows.  I think it to be particularly ominous for the Baltimore prosecution in light of the final phrase, emphasizing that the police are given wide latitude in assessing the circumstances confronting them.  And Freddie Gray was no stranger to the police.

Perhaps the central teaching of our decisions bearing on the probable-cause standard is that it is a "practical, nontechnical conception." Brinegar v. United States, 338 U.S. 160, 176 (1949). "In dealing with probable cause, . . . as the very name implies, we deal with probabilities. These are not technical; they are the factual and practical considerations of everyday life on which reasonable and prudent men, not legal technicians, act.' Id., at 175. Our observation in United States v. Cortez, 449 U.S. 411, 418 (1981), regarding "particularized suspicion," is also applicable to the probable-cause standard:

"The process does not deal with hard certainties, but with probabilities. Long before the law of probabilities was articulated as such, practical people formulated certain common-sense conclusions about human behavior; jurors as factfinders are permitted to do the same - and [462 U.S. 213, 232]   so are law enforcement officers. Finally, the evidence thus collected must be seen and weighed not in terms of library analysis by scholars, but as understood by those versed in the field of law enforcement."