Island Intellectual Property LLC v Deutsche Bank AG, 2012 U.S. Dist. LEXIS 21742 (S.D.N.Y. Feb. 14, 2012):

In determining where to draw appropriate lines, the court must consider whether an expert's proposed testimony would usurp the province of the judge to instruct on the law, or of the jury to make factual determinations. See United States v. Bilzerian, 926 F.2d 1285, 1294 (2d Cir. 1991); Marx & Co. v. Diner's Club, Inc., 550 F.2d 505, 510-11 (2d Cir. 1977). It is also inappropriate for experts to act as mere conduits for others' hearsay, Wantanabe Realty Corp. v. The City of New York, No. 01 Civ. 10137(LAK), 2004 WL 188088, at *2 (S.D.N.Y Feb. 2, 2004), or as vehicles for factual narrative, see Highland Capital Mgmt., 551 F. Supp. 2d at 187; In re Rezulin Products Liability Litig., 309 F. Supp. 2d 531, 551 (S.D.N.Y. 2004).

PRINCIPLES

***[T]he Court sets out the following principles to guide the parties' presentation of expert testimony at trial, in addition to ruling on the specific motions in limine. The Court expects that the parties will modify their direct and cross-examinations to accord with these principles as well as the specific rulings below.

Principle 1: No proposed expert will be allowed to provide any opinion or statement regarding what he believes or assumes the law to be. For instance, no proposed expert will be allowed to state his view that in order to be valid, a patent must not be obvious and must be written with sufficient definiteness. ***

Principle 2: No proposed expert will be allowed to opine on the state of mind or intent of a particular individual. This invades the province of the jury members, who are tasked with determining facts and credibility. In re Blech Sec. Litig., 2003 WL 1610775, at *21-22; Highland Capital Mgmt., 551 F. Supp. 2d at 187-88.

Principle 3: No proposed expert will be allowed to act as a vehicle for lengthy factual narrative. Highland Capital Mgmt, L.P., 551 F. Supp. 2d at 187-88; In re Rezulin Products Liability Litig., 3 09 F. Supp. 2d at 551. To the extent that the parties want to place admissible documents or deposition testimony of percipient witnesses before the jury, they can offer the documents, call the witnesses in the ordinary course, or designate and publish the deposition testimony as appropriate. This Court will not allow a proposed expert to walk the jury through a narrative of the numerous documents produced during discovery or, for instance, a timeline of the patent prosecution events. This is a particularly important principle for the parties to grasp, since several of the proposed experts' reports contain lengthy descriptions of the documentary record. An expert may offer opinions that will help the jury understand the evidence or determine factual issues. He may not, however, directly transmit facts to the jury, about which he has no personal knowledge, simply because his testimony represents the easiest way to do that. The proposed expert may refer to documents he has reviewed and — to the extent that they have already been admitted into evidence — show particularly relevant passages to the jury, but must stop short of simply summarizing their contents in narrative form. That would inappropriately transform an expert, without firsthand knowledge, into a quasi-fact witness.

Principle 4: The Court will closely monitor the relevance of documents and testimony. Fed. R. Evid. 401, 402. This is a case about four patents and five claims — it is by no means as large a case as it once was. The parties understand what is truly relevant to whether the patents are valid and enforceable, whether they have been infringed and, if so, what the damages might be. Matters extraneous to those issues shall be excluded.

Principle 5: The evidence presented at trial — expert or otherwise — should be directed only to proving the applicable causes of action and defenses related to the remaining four patents and five claims in this action, nothing else.