Over the years, I have commented on many cases where courts reverse criminal convictions due to inappropriate comments by overzealous prosecutors; but I don't remember having read about a similar result in a civil case. For that reason, here is an interesting story out of the ABA Journal Online about a Florida judge who declared a mistrial in a tobacco case and ordered the defendant's lawyer to show cause why he shouldn’t have to pay sanctions for the cost of a retrial. According to the story, in questioning an expert witness, the lawyer affirmed that a jury in a different case had found how many cigarettes a person had to smoke daily in order to become addicted. The judge reacted to this for more than one reason, the most important being that the statement was not true.
In addition to causing the mistrial and, perhaps costing the lawyer the bill for the retrial, if the statement was false, the lawyer could be found to have violated, at least, rules 4.1 and 8.4.