Edward K. Cheng

Introduction

Recent voices in the evidence literature have expressed alarm over deepfake technologyAI-driven algorithms that can manufacture fictitious images and audio that are difficult to distinguish from reality. These voices for reform claim that deepfakes represent a sea-change in technology that threatens to upend the legal proof process. The problem lies not only in deepfakes’ ability to mislead and confuse, but also in the technology’s pervasiveness and ease of use.

Are these fears over deepfakes justified? Does the legal system need to adopt new authentication rules and approaches to address their threat? In this Essay, I argue that the answer is no, but more significantly, I use deepfakes as a vehicle to explore the nature of authentication and, more generally, legal proof. My argument proceeds in three related steps: First, I propose a tentative model of evidentiary authentication based on base rates of trust. Such a base rate model suggests that existing evidentiary principles of authentication are more than sufficient to address the problem of deepfakes, particularly as the public becomes aware of and exposed to their existence and dangers. Second, the authentication problem of deepfakes parallels the legal system’s angst over photographs a century ago. Indeed, the compromises that the legal system made to handle photographs and other images provide a ready framework for thinking about and addressing the deepfake problem. Finally, I raise some broader implications of taking a trust model of evidence seriously. On the one hand, a theory of legal proof based on trust may illuminate evidentiary problems like authentication. On the other hand, a trust theory of proof lays bare some troubling realities. If legal proof is ultimately about trust, what happens to information sources that certain factfinders are inclined to distrust, and what will this mean in an increasingly polarized society?

Professors Bierschbach and Stein’s observation that evidentiary rules mediate the age-old tension between retribution and deterrence is both fascinating and thought provoking. The idea that the two hitherto balkanized fields are inextricably linked in this quirky but productive way is surely an impressive insight that will force criminal law and evidence scholars never again to look at their respective fields in quite the same way. In this Response, I want to focus on the broader normative question raised by their thesis—whether the legal system should use evidentiary rules to achieve substantive reform. Conveniently for me, I can leave the task of probing the relationship between the Bierschbach-Stein thesis and general criminal law theory to more qualified scholars, like my colleague Professor Mike Cahill.

So “[a]re mediating rules a virtue or a vice?” On this question, Bierschbach and Stein are nominally agnostic. For example, careful not to overstate their case, they acknowledge that such special evidentiary rules “might . . . be seen as illegitimately thwarting the accepted processes for resolving political agreement.” Put plainly, they recognize that evidentiary rules so conceived can become Trojan horses. The overall tenor of their essay and longer article, however, takes a somewhat rosier view. They emphasize the ability of mediating rules to facilitate compromise and “promote a rough social consensus around criminal law in a moral universe that is diverse and pluralistic.”

I am far more skeptical. The use of evidentiary rules to achieve substantive goals strikes me as a Faustian bargain, and, given Bierschbach and Stein’s acknowledgedly tentative position, I hope to dissuade them of the virtues of the practice. My goal therefore is to explore briefly the potential dark side of specialized evidentiary rules. The concerns of injecting substantive goals into evidence law extend far beyond the narrow legitimacy concerns Bierschbach and Stein raise. It is not simply the question of whether we aspire to a pluralistic or majority-take-all democratic society. Rather, evidentiary manipulation threatens the legitimacy of criminal and evidence law.

Deepfakes, Photographs, and Trust in Evidence

The Perils of Evidentiary Manipulation