Justice William C. Koch referenced an article by Joseph H. King, Jr. about per diem arguments in his concurring opinion in Elliott v. Cobb, W2009-00961-SC-S09-CV (Sept. 23, 2010). Elliott recognized that lawyers in medical malpractice cases tried in Tennessee have a right to argue the monetary value of the case but cannot argue the amount sued for in the ad damnum. Here is the majority opinion by Justice Sharon Lee. Justice Koch’s concurrence made it clear that the Court was not addressing the issue of the appropriateness of per diem arguments.
Professor King’s article is copywright protected so I cannot share it with you. You can order the entire article on Westlaw or through the University of Tennessee Law Review. The title of the article is "Counting Angels and Weighing Anchors: Per Diem Arguments For Noneconomic Personal Injury Tort Damages." It can be found at 71 Tenn. L. Rev. 1 (Fall 2003).
You can get a feel about the article from this language quoted from the article’s Conclusion: "More fundamentally, per diem anchoring exacerbates the ill-defined nature of damages for pain and suffering. In so doing, per diem anchoring undermines the central goals of tort law."