In a Massachusetts criminal case, the jury consists of either six of twelve jurors. After a trial, a defendant cannot be convicted unless all jurors unanimously agree that the defendant was guilty of the crimes charged. Thus, if even one juror believes that a defendant is not guilty, the court will declare a mistrial, and the defendant will avoid a conviction. For this reason, the jury selection process in Massachusetts criminal trial is critical.
The history of jury-selection practices across the United States is an unfortunate one. While the jury-selection process allows prosecutors and defendants to strike jurors from the panel who they believe will favor the other side through what is called a peremptory strike, there are limits on the exercise of these peremptory strikes.
One of the most fundamental rights any criminal defendant enjoys is the right to be tried by a jury of their peers. This right, embodied in the Sixth Amendment, requires that a jury be drawn from a fair cross-section of society. Thus, in the case, Batson v. Kentucky, the U.S. Supreme Court held that the prosecution cannot use their peremptory strikes to eliminate jurors based on their race. Since then, the Court has considered numerous other cases involving race-based selection techniques, most recently with the case Flowers v. Mississippi.