The concept of the "thirteenth juror" rule in Tennessee criminal law refers to the trial court judge's responsibility to consider the weight of the evidence from a criminal trial after the jury has returned a guilty verdict. If the judge then disagrees that the weight of the evidence supports that guilty verdict, the judge, as "thirteenth juror," must grant the defendant a new trial (with a different judge). This is actually just a unique and specialized role of the trial court judge and does not mean the judge is part of the jury. In addition, as noted in the recent case of State v. Stewart, M2014-00074-CCA-R3-CD (Tenn.Crim.App. 5-22-2015), the accuracy of the judge's decision as "thirteenth juror" is not reviewable on appeal (though statements in the record indicating the judge misconstrued the authority granted by the rule could result in appellate relief).
In the Stewart case, the defendant was convicted at trial of attempt to commit sexual battery. One of the claims on direct appeal was that the trial court failed to exercise its role as "thirteenth juror" and that the trial court should have, pursuant to that role, disagreed with the verdict and ordered a new trial. The Court of Criminal Appeals disagreed, noting that the trial court does not have to state its "juror" ruling. It is legally presumed that an order overruling a motion for new trial expresses approval of the jury verdict. Furthermore, the merit of the ruling is not a question reviewable on appeal. Sufficiency of the evidence is reviewable on appeal. The decisions of the jurors and of the trial court judge regarding the weight of the evidence are not.
In 2014, the Tennessee State Legislature passed the Chris Newsom Act, which, now in effect, creates a presumption that the trial court judge has approved and agreed with the verdict at the moment the judge dismisses a jury which has rendered a verdict. So while the trial court judge may still consider the weight of the evidence at a motion for new trial hearing, the presumption now is that the judge has already done that and agrees with the jury, once that jury has been dismissed.
It should still be mentioned that the rule does not grant the trial court judge the authority to grant a new trial in a situation where the jury has rendered a verdict of not guilty and the trial court judge disagrees with that verdict. Despite the name of the rule, the trial court judge does not deliberate with the jury, has access to more information about the case than does the jury, and only exercises a "juror" role once the actual jury reaches a guilty verdict (and has no such role at all on counts for which the jury reaches a not guilty verdict).
For information about the respective roles of a judge and jury in a criminal case, contact Hindman & Associates.