Law Commons^™

Power And Statistical Significance In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach

All Faculty Scholarship

Event studies, a half-century-old approach to measuring the effect of events on stock prices, are now ubiquitous in securities fraud litigation. In determining whether the event study demonstrates a price effect, expert witnesses typically base their conclusion on whether the results are statistically significant at the 95% confidence level, a threshold that is drawn from the academic literature. As a positive matter, this represents a disconnect with legal standards of proof. As a normative matter, it may reduce enforcement of fraud claims because litigation event studies typically involve quite low statistical power even for large-scale frauds.

This paper, written for …

Controlling The Jury-Teaching Function, Richard D. Friedman

Articles

When evidence with a scientific basis is offered, two fundamental questions arise. First, should it be admitted? Second, if so, how should it be assessed? There are numerous participants who might play a role in deciding these questions—the jury (on the second question only), the parties (through counsel), expert witnesses on each side, the trial court, the forces controlling the judicial system (which include, but are not limited to, the appellate courts), and the scientific establishment. In this Article, I will suggest that together, the last two—the forces controlling the judicial system and the scientific establishment—have a large role to …

The Incompatibility Of Due Process And Naked Statistical Evidence, G. Alexander Nunn

Faculty Scholarship

Numerous articles and commentaries have grappled with an undeniable feeling of injustice that comes from wrestling with naked statistical evidence. Even if, from a purely quantitative standpoint, the weight of the evidence supports the imposition of liability on a defendant, the sole use of probabilities to assess this liability seems innately unfair. This tension has spawned a great debate that questions the role of naked statistical evidence in today’s legal system. Contributing to this discourse, this Note argues that, in certain circumstances, the use of naked statistical evidence constitutes a due process violation. United States circuit courts have held that …

When 10 Trials Are Better Than 1000: An Evidentiary Perspective On Trial Sampling, Edward K. Cheng

Vanderbilt Law School Faculty Publications

In many mass tort cases, separately trying all individual claims is impractical, and thus a number of trial courts and commentators have explored the use of statistical sampling as a way of efficiently processing claims. Most discussions on the topic, however, implicitly assume that sampling is a “second best” solution: individual trials are preferred for accuracy, and sampling only justified under extraordinary circumstances. This Essay explores whether this assumption is really true. While intuitively one might think that individual trials would be more accurate at estimating liability than extrapolating from a subset of cases, the Essay offers three ways in …

Will Quants Rule The (Legal) World?, Edward K. Cheng

Vanderbilt Law School Faculty Publications

Professor Ian Ayres, in his new book, Super Crunchers, details the brave new world of statistical prediction and how it has already begun to affect our lives. For years, academic researchers have known about the considerable and at times surprising advantages of statistical models over the considered judgments of experienced clinicians and experts. Today, these models are emerging all over the landscape. Whether the field is wine, baseball, medicine, or consumer relations, they are vying against traditional experts for control over how we make decisions. For the legal system, the take-home of Ayres's book and the examples he describes is …

Revisiting 'Dreyfus': A More Complete Account Of A Trial By Mathematics, David H. Kaye

Journal Articles

Legal literature and case law depicts the infamous conviction of Alfred Dreyfus for treason and espionage in 1899 as a prime example of the irresistible power of even grossly fallacious mathematical demonstrations to overwhelm a legal tribunal. This essay shows that Dreyfus is not a case of mathematics run amok, unchecked and uncomprehended. To the contrary, the defects in the mathematical proof were dramatically exposed, and this evidence did not lead Dreyfus's judges to condemn him. This history undercuts the reliance of modern courts and commentators on Dreyfus as an indication or illustration of the alleged dangers of probability evidence …

Sometimes What Everybody Thinks They Know Is True, Richard D. Friedman, Roger C. Park

Articles

This essay responds to D. Davis and W. C. Follette (2002), who question the value of motive evidence in murder cases. They argue that the evidence that a husband had extramartial affairs, that he heavily insured his wife's life, or that he battered his wife is ordinarily of infinitesimal probative value. We disagree. To be sure, it would be foolish to predict solely on the basis of such evidence that a husband will murder his wife. However, when this kind of evidence is cobmined with other evidence in a realistic murder case, the evidence can be quite probative. We analyze …

Dna As Evidence: Viewing Science Through The Prism Of The Law, Peter Donnelly, Richard D. Friedman

Articles

In this article, we analyze a problem related to DNA evidence that is likely to be of great and increasing significance in the near future. This is the problem of whether, and how, to present evidence that the suspect has been identified through a DNA database search. In our view, the two well-known reports on DNA evidence issued by the National Research Council (NRC) have been badly mistaken in their analysis of this problem. The mistakes are significant because the reports have carried great authority with American courts; moreover, the DNA Advisory Board of the FBI has endorsed the second …

Dna Database Searches And The Legal Consumption Of Scientific Evidence, Peter Donnelly, Richard D. Friedman

Articles

DNA evidence has transformed the proof of identity in criminal litigation, but it has also introduced daunting problems of statistical analysis into the process. In this Article, we analyze a problem related to DNA evidence that is likely to be of great and increasing significance in the near future. This is the problem of whether, and how, to present evidence that the suspect has been identified through a DNA database search. In our view, the two well-known reports on DNA evidence issued by the National Research Council ("NRC"), each of which has carried great authority with the American courts on …

Assessing Evidence, Richard D. Friedman

Reviews

David A. Schum's Evidential Foundations of Probabilistic Reasoning, 2 C.G.G. Aitken's Statistics and the Evaluation of Evidence for Forensic Scientists,3 and Bernard Robertson and G.A. Vignaux's Interpreting Evidence: Evaluating Forensic Science in the Courtroom4 all have something to tell us about how to use and evaluate evidence. Although the books are addressed to different primary audiences5 and their authors come from a variety of disciplines and from distant points of the English-speaking world,6 all three help draw the connection between underlying theory and presentation in the courtroom. Though Schum uses numerous examples from litigation and discusses the legal literature of …

Probability And Proof In State V. Skipper: An Internet Exchange, Ronald J. Allen, David J. Balding, Peter Donnelly, Richard D. Friedman, David H. Kaye, Lewis Henry Larue, Roger C. Park, Bernard Robertson, Alexander Stein

Articles

This is not a conventional article. It is an edited version of messages sent to an Internet discussion list. The listings begin with the mention of a recent opinion of the Connecticut Supreme Court, parts of which are reproduced below. The listings soon move to broader issues concerning probability and other formal systems, their limitations, and their uses either in court or as devices for understanding legal proof.

Stories Versus Theories At The Cardozo Evidence Conference: It's Just Another Metaphor To Me, Lewis H. Larue

Scholarly Articles

Not available.

Statistical Significance And The Burden Of Persuasion, David H. Kaye

Journal Articles

In most endeavors concerned with the acquisition of knowledge, quantitative information is welcomed. In law, however, it appears sometimes that scientific or numerical evidence makes cases harder, not easier. Nevertheless, there are many cases and administrative proceedings, in such areas as environmental law, food and drug regulation, and civil rights, in which statistical data obtained by observation or experiment are readily accepted as assisting in the proper resolution of disputed issues of fact. When courts or administrators confront scientific and statistical evidence in these proceedings, they are not always certain of how to weigh the evidence or whether they should …