What the law protects
Two protections sit behind every jury verdict. The first is the privacy of the jury room: what jurors say to each other while deciding is, as a rule, not something a court will later open up. The second is the verdict itself. A not-guilty verdict is final, and a juror is not called to account for returning one. Those two rules exist in some form in every jurisdiction this guide covers. Their exact form, and their exceptions, are in each chapter.
What it does not protect
The protections are about the verdict. They are not about getting onto the jury. During selection, a person is asked questions under oath, and the answers matter. A person who tells the court they will not follow its instructions can be excused for that reason, and the law in every jurisdiction allows the court to excuse a person for cause. The grounds, and how far a juror's views about the law itself count as one, are set out in each chapter.
The protections also do not reach outside the jury room. What a juror does during a trial, apart from deciding, is governed by the judge's instructions about reading, talking and looking things up, and those instructions carry consequences.
The line
There is a line that every jurisdiction draws, and it is not between guilty and not guilty. It is between a juror deciding a case and anyone trying to influence a juror from outside the trial. Approaching, pressuring or paying a juror is a crime everywhere this guide looks, and the laws that say so are written in terms that do not depend on which way the juror was pushed.
That is also the line this guide keeps. It explains what the law says about jurors. It does not tell anyone how to decide a case, and it is not for contacting a juror in a case that is pending.
Where your state draws it
The two protections, the grounds for excusing a juror, and the law on interfering with one are all written differently from state to state. One state's rule on what a juror may say after the verdict is a sentence; another's is a page with exceptions. The chapter for your state sets out each of them in the state's own words, with the citation.