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108 Ky. L.J. 239 (2019-2020)
Res Ipsa Loquitur: Reducing Confusion or Creating Bias?

handle is hein.journals/kentlj108 and id is 259 raw text is: 




            RES IPSA LoQuiTuR: REDUCING CONFUSION
                             OR CREATING BIAS?

                       Jeffrey H. Kahn' & John E. Lopatka'

                                    ABSTRACT

     The so-called doctrine of res ipsa loquitur has been a mystery since its birth
more than a century ago. This Article helps solve the mystery. In practical effect,
res ipsa loquitur, though usually thought of as a tort doctrine, functions as a rule of
trial practice that allows jurors to rely upon circumstantial evidence surrounding an
accident to find the defendant liable. Standardjury instructions in negligence cases,
however, inform jurors that they are permitted to rely upon circumstantial evidence
in reaching a verdict. Why, then, is another, more specific circumstantial evidence
charge necessary or desirable?
    We describe and evaluate the arguments that have been made in support of and
 in opposition to the res ipsa instruction. One theory is that jurors are confused in
 performing their task when given only standard instructions; the charge, therefore,
 clarifies their task, thereby improving the quality of their decisionmaking.
 A competing theory is that the instruction biases jurors in favor ofplaintiffs, thereby
 degrading the quality of decisionmaking. Our theoretical analysis concludes that
 the bias explanation is stronger. We reach this conclusion by applying for the
first-time modern learning on cognition to the res ipsa instruction.
    To support our theoretical conclusion, we report the results of experiments
designed to determine the effects of the instruction. All these experiments were
intended first to confirm that the res ipsa instruction has an effect and second to
confirm or refute our theoretical conclusion that the instruction biases rather than
clarifies. While the empirical results did not demonstrate bias, they also failed to
show the absence of bias. Moreover, we found no evidence that the instruction
reduces confusion. Our conclusion is that the charge has no positive effect, and
either may create a bias or, at best, is meaningless.


     Harry W. Walborsky Professor of Law, Florida State University, College of Law
     A. Robert Noll Distinguished Professor of Law, Penn State Law, Pennsylvania State University, University
Park. The authors would like to thank Mary McCormick and Sarah Carter for their helpful research on this Article
and Professor Justin Sevier for his insightful comments and suggestions on prior drafts.

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