Criminal Innovation and the Warrant Requirement: Reconsidering the Rights-Police Efficiency Trade-Off

III. AN ECONOMIC MODEL OF CRIMINAL INNOVATION AND THE WARRANT REQUIREMENT This Part provides an economic model that demonstrates when the Police Efficiency Assumption will fail, or when LEOs will not be better be off in terms of their ability to catch criminals, if they are not required to obtain a warrant for an investigation than they would be if a warrant were required. To make this assessment, we analyze law-enforcement decisions in two different scenarios: one, under the "Warrant" condition, when a court has determined that a particular investigation is a search; the other, under the "Nonwarrant" condition, when a court has determined that the investigation is a nonsearch. For example, if a court finds that an investigative practice that LEOs widely consider to be a search is in fact a nonsearch, or vice versa, we can compare the effect of the rule change on police efficacy: if LEOs do not gain from the change away from the warrant requirement, the Assumption fails. In economic language, the Assumption fails if officers' expected utility (175) under the Warrant condition is greater than or equal to that in the Nonwarrant condition. Economic models enable us to formalize the incentives of both criminals and LEOs, and to examine the effect of different rules on their predicted behavior. Specifically, we use a game-theoretic model because we need to examine the decisions of both LEOs and the criminal as they influence each other. (176) The likelihood that LEOs will conduct an investigation depends upon the amount of innovation by criminals, because the latter impacts the chances that an investigation will find evidence. Likewise, the incentives for criminals to innovate will increase when LEOs are more likely to conduct an investigation. The utility of each actor depends on both its own decisions and those of the other actor. Most analyses of criminal innovation have not taken this approach and have simply looked at the criminal's decision whether to innovate. (177) These papers have treated a criminal's likelihood of being caught as a function of the amount of criminal innovation and the amount of resources society devotes to detecting crime. However, this view overlooks the fact that the decision by LEOs to investigate a particular crime is not fixed, but rather depends on the likelihood that an investigation will be successful--in other words, that it will reveal admissible evidence. Increased criminal innovation leads not only to a smaller chance of LEOs finding evidence if they conduct an investigation, but also to a smaller likelihood that LEOs will investigate at all, given the fact that they know criminals may innovate. (178) Thus, it is crucial to look at both of these effects when analyzing a criminal's decision whether to innovate. (179) This Part begins by discussing the variables that influence the decision by law enforcement whether to search and the decision by the criminal whether to innovate. It then lays out the games and solves them to determine the likelihood that LEOs will search and that the criminal will innovate. We are then able to specify the conditions under which the Police Efficiency Assumption fails. A. Criminal Utility Criminals act to maximize the utility gained from their crime. The model used here to analyze criminal decision making is adapted from the Becker model of crime. (180) That model analyzes a person's decision regarding the amount of crime to commit, comparing the benefits from crime to the expected cost of committing crime--the probability of detection multiplied by the punishment that comes with detection. (181) Our model is similar to Becker's model, but includes some important changes. First, we assume that the criminal has committed or is going to commit a single isolated crime. This means that the criminal's only decision is whether to innovate to cover up the crime. This assumption is in accord with what could be termed a "career criminal" or a "sophisticated criminal," who will definitely engage in a certain crime. …