When a jury finds a defendant not guilty of a crime, it hasn’t necessarily determined that he or she is innocent. All the acquittal does, in legal terms, is establish that the prosecution didn’t prove beyond a reasonable doubt that the defendant is guilty. In fact, an acquittal is entirely appropriate if jurors believe the defendant committed the crime but aren’t close to certain. In that way, an acquittal doesn’t amount to actual vindication.
Example: In 2013, a six-person jury acquitted former neighborhood-watch volunteer George Zimmerman of murder and manslaughter charges relating to the shooting death of 17-year-old Trayvon Martin. After the verdict, one of the jurors said that there simply wasn’t enough evidence to convict: “You can’t put the man in jail even though in our hearts we felt he was guilty.” (See A Reasonable Doubt.)