I'm looking for an online citation, but it is true that the grounds for appeal (in a global sense, not that such grounds stand in this case) does include juror and jury activities.
In an earlier message, you refered to "District courts" as not being the same as Federal Courts. The case noted by Bluntpoint was a case in a Federal District Court.
Here is a case, heard in Federal Court, where juror misconduct was raised as grounds for a new trial: Mistrial? Rosenthal Jurors Say They Received Outside ...
Tim McVeigh's counsel also argued for a new trial based on juror misconduct. CNN - Appeals court considers McVeigh's bid for new trial
Here is a broader reference: JURY MISCONDUCT AND POST TRIAL JUROR INTERVIEWS