The runaway jury - John Grisham

Every jury has a leader, and the verdict belongs to him.

In Biloxi, Mississippi, a landmark trial with hundreds of millions of dollars at stake begins routinely, then swerves mysteriously off course. The jury is behaving strangely, and at least one juror is convinced he’s being watched. Soon they have to be sequestered. Then a tip from an anonymous young woman suggests she is able to predict the jurors' increasingly odd behaviour.

Is the jury somehow being manipulated, or even controlled? If so, by whom? And, more importantly, why?