How does Scout know that Tom has not been acquitted even before the jury reports in "To Kill a Mockingbird"?

As Scout is waiting with the people gathered in the courthouse for the jury to finish its deliberations, she experiences an "impression...creeping into (her)...not unlike...winter...and (she) shiver(s), though the night (is) hot".  Although Jem is ebullient, confident that, on the basis of the evidence presented, Tom will be acquitted, Scout senses an atmosphere in the courtroom that is "exactly the same as a cold February morning, when the mockingbirds (are) still...deserted, waiting, empty...(even though) the courtroom (is) packed with people".  Scout's dismal feelings of foreboding are confirmed for her when the jury walks in and "not one of them (looks) at Tom Robinson".  As her father's daughter, Scout understands something that only "a lawyer's child could be expected to see...(that) a jury never looks at a defendant it has convicted".  When the members of the panel call out "guilty" one by one, Jem is shocked and devastated at the inexplicable injustice of the verdict, but for Scout, it is only a validation of something she already knew was coming (Chapter 21).