Probability Thresholds

AuthorJonathan S. Masur
PositionBigelow Fellow and Lecturer in Law, University of Chicago Law School
Pages1295-1357

    Bigelow Fellow and Lecturer in Law, University of Chicago Law School. I thank Douglas Baird, Frederic Bloom, Rachel Brewster, John Bronsteen, David Fagundes, Thomas Miles, Richard Posner, Eric Posner, Adam Samaha, Geoffrey Stone, Lior Strahilevitz, Cass Sunstein, Lesley Wexler, and participants in the Chicago Junior Faculty Workshop and Chicago Works in Progress seminar for their helpful comments and suggestions on earlier drafts.

Page 1295

"Independent and impartial judges must assess the balance between protecting our liberties and protecting our national security."

- Judge Samuel A. Alito Jr.1

"We have to deal with this new type of threat in a way we haven't yet define . . . .

With a low-probability, high-impact event like this . . . .

. . . If there's a one percent chance that Pakistani scientists are helping al Qaeda build or develop a nuclear weapon, we have to treat it as a certainty in terms of our response . . . ."

- Vice President Dick Cheney2

I Introduction

The First Amendment states that Congress "shall make no law . . . abridging the freedom of speech,"3 but since the days of Justice Hugo Black's absolutism,4 few have doubted that the First Amendment must yield when its enforcement would threaten dire harm to the nation or its security. As the Supreme Court famously remarked, the Constitution "is not a suicide pact."5 Likewise, the Court's canonical speech-versus-security hypothetical that "[n]o one would question but that a government might prevent . . . the publication of the sailing dates of transports or the number and location of troops"6 has forfeited no currency in the seventy-five years since it was written.

Among courts and scholars, the debate over the proper balance between speech freedoms and national security has most often centered on the question of what framework judges should employ when deciding whether the threat to security posed by some form of expression is so great that the First Amendment no longer protects its utterance. In quotidian First Amendment cases that do not involve potentially grave national harms (cases of political speech or artistic expression, for instance), there is certainly little consensus or uniformity, and courts apply a variety of methods and doctrinal rules.7 But in difficult cases that place the freedom ofPage 1296 speech and the demands of national security in direct opposition, a single leading view has emerged. The approach that has come to predominate, both within the academy and among the lower courts-though, importantly, not the Supreme Court-is "cost-benefit analysis,"8 a methodological tool borrowed from the private-law and regulatory contexts.9 This Article urges a rethinking of this approach.

Cost-benefit analysis demands that the judge simply and straightforwardly balance the cost of the dangerous speech-the harm that the expression is likely to cause if it is allowed-against the benefit (a better-informed public, for instance) one might expect the speech to produce; the speech warrants constitutional protection if (and only if) its benefits outweigh its costs. The aspiration for practitioners of cost-benefit analysis, even in the realm of inchoate constitutional rights, has been to quantify these costs and benefits to the greatest possible degree. This analysis requires the judge to determine the approximate probability that a potential speech-borne threat will materialize, estimate the magnitude of the damage that threat might cause, and multiply the probability and magnitude to arrive at the expected outcome of permitting the speech to occur. This outcome is then compared with the benefit that the judge expects the speech to confer. Consider, for instance, the publication of the sailing date of a troop transport, as mentioned above. If the government asserts that a newspaper publication of this date would create a five-percent probability that a submarine will sink the transport, and if the transport carried one hundred people, then the likely outcome of allowing publication of its sailing date will be five deaths. Only if the speech is worth more than five lives will the Constitution protect it.

This view of the First Amendment is not entirely without controversy.10 Nonetheless, one fact has become inescapable: cost-benefit analysis is ascendant within both the lower courts and the legal academy, and courts now decide cases that arise at the intersection of individual liberty and national security almost exclusively with reference to such a weighing of interests.11 This development is hardly surprising given the intuitive appeal of the approach. It would be a strange constitutional doctrine indeed thatPage 1297 forced courts to allow behavior that proves, in the aggregate, harmful (or even very harmful) to the nation's interests.

Yet somehow the First Amendment has tread a different path-a desirable one, as this Article will assert. First Amendment doctrine, as expounded by the Supreme Court, contains within it a peculiar twist, a previously unnoticed determination not to conduct unadulterated cost-benefit analysis. Where one might expect the First Amendment to advocate straightforward balancing-benefits versus harms-the doctrine instead inserts what this Article will refer to as a "probability threshold": a lower boundary on how likely a potential harm must be in order for that harm to register in the constitutional calculus, regardless of the harm's magnitude. If an event is so unlikely that the probability that it will occur does not cross this threshold, First Amendment doctrine instructs courts to refuse to weigh the expected harm from the event against the benefits that the speech in question is likely to produce. True balancing-a full accounting on each side of the ledger-simply will not take place unless the probability of the asserted harm crosses the threshold.

Consider a variant of this "troop transport" hypothetical. A magazine seeks to publish an article describing the production of a nuclear weapon, and the government estimates that the slight aid this article might provide to a terrorist group seeking to develop such a weapon will increase the likelihood that New York City and its 10 million residents are destroyed in a nuclear blast by a probability of 1 in 2 million (0.00005%). Again, the statistically expected outcome is five deaths. But here the threat is of such miniscule probability that it likely falls below the probability threshold, and therefore, it cannot serve as justification for censoring the article, regardless of how devastating such an attack would be. Threats that straightforward cost-benefit balancing would treat as equivalent fare very differently under the probability threshold.

This Article thus urges a rethinking of the approach that scholars and lower courts have taken to this crucial class of speech-versus-security cases. Moreover, the Article attempts to account for such a significant (though well-hidden) anomaly within such a venerable doctrine. In so doing, it turns to behavioral law and economics for insight into the cognitive processes that surround these instances of constitutional decision-making. The "probability threshold" may at first glance appear dramatically over-inclusive, denying the government the constitutional authority to combat highly dangerous, highly unlikely threats that speech might trigger. But the institutional relationship between the courts and the executive, and indeed the very nature of low-probability dangers, renders such a threshold a necessary corrective to what would otherwise be systematic overestimation of speech-borne perils.

As the Article explains below, three mutually reinforcing factors conspire to exaggerate the importance of low-probability, high-magnitudePage 1298 threats. First, the government-in its joint role as both partisan litigant and ostensible purveyor of neutral information-will tend to inflate the risks, particularly the low-probability risks, posed by the speech it attempts to stifle. The history of the government's efforts to curb undesired speech is characterized by such exaggerations. Second, individuals-both judges and jurors-have a propensity to overvalue the danger of low-probability risks and ignore many differences in low-probability estimates, resulting in a willingness to...

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