The answer is: It is very hard as it should be because the jury trial is a Constitutional right.
Here are some quotations that I assembled from the Massachusetts Supreme Judicial Court and the Appellate Court in Massachusetts.
STANDARD FOR OVERTURNING A JURY:
The standard for granting JNOVs is whether “anywhere in the evidence, from whatever source derived, any combination of circumstances could be found from which a reasonable inference could be drawn in favor of the plaintiff.’ ” Raunela v. Hertz Corp., 361 Mass. 341 , 343 (1972), quoting from Kelly v. Railway Exp. Agency, Inc., 315 Mass. 301
“If any such combination of circumstances could be found it is . . . immaterial how many other combinations could have been found which would have led to conclusions adverse to the plaintiff.” Kelly v. Railway Express Agency, Inc., 315 Mass. 301, 302 (1943). Quoted in Brewster Walcovering Co vs. Blue Mountain Wallcovering, 68 Mass App. Ct 582., 2007.
“Evidence that contradicts the testimony of the nonmoving party is to be ignored.” Conway v. Smerling, 37 Mass. App. Ct. at 3, citing Bennett v. Winthrop Community Hosp., 21 Mass. App. Ct. 979 , 982 (1986).
“It is unavailing for a defendant to argue there was evidence warranting a contrary finding by the jury”. Curtiss-Wright Corp. v. Edel-Brown Tool & Die Co., 381 Mass. 1, 4 (1980).
“We give deference to decisions of a trier of fact who is usually in a superior position to appraise and weigh the evidence”. Buster v. George W. Moore, Inc., 438 Mass. 635 , 642 (2003)
“Nor may the court substitute its judgment of facts for that of the jury” Wright & Miller, Federal Practice and Procedure Section 2524, at 543-544 (1971). Smith & Zobel, Rules Practice Section 50.6, at 203 (1977).
“We do not consider weight and credibility of the evidence”. Sahagan v. Commonwealth, 25 Mass. App. Ct. 953 , 953 (1988).
“Judgment notwithstanding the verdict is to be granted cautiously and sparingly”. Phelan v. May Dept. Stores Co., 60 Mass. App. Ct. 843, 844 (2004),
“An appellate court will not set aside a jury verdict on any material fact found by a jury unless the jury verdict or fact has no rational basis in the evidence.” Brewster Walcovering Co vs. Blue Mountain Wallcovering, 68 Mass App. Ct 582., 2007.
“A party may not raise an issue in a motion for judgment n.o.v. that was not raised in a motion for directed verdict”. Shafir v. Steele, 431 Mass. 365, 370 (2000); Furthermore, a motion for a directed verdict according to Mass.R.Civ.P. 50(a), 365 Mass. 814 (1974), must “state the specific grounds therefor”.
“In reviewing the denial of the defendant[s’] motions for directed verdict and judgment notwithstanding the verdict, we will construe the evidence most favorably to the plaintiff and disregard that favorable to the defendant[s].” Cimino v. Milford Keg, Inc., 385 Mass. 323, 326 (1982). See Dartt v. Browning-Ferris Indus., Inc. (Mass.), 427 Mass. 1, 16 (1998).