Evidence law controls what information will be admissible in court and when, how, and by whom it may be presented. It shapes not only the trial decisions of lawyers, judges, and juries, but also many other pretrial and trial decisions and behaviors – for example, by police (whether to initiate a search) and defendants (whether to take a plea deal). Even when the relevant evidence law is known, these decisions are made under great uncertainty. Parties often do not know whether key evidence will be admissible at trial, cannot know how jurors will react to evidence, and, particularly in the criminal context, may not know what evidence their adversary possesses. With all these applications and uncertainties, understanding how legal decisions are made depends on understanding both evidence law itself and the human reasoning processes that created and use it. This chapter thus describes the interplay of evidence law and decision-making across a variety of legal settings and, accordingly, makes frequent references to other chapters in this book.

Expert testimony concerning risk and its communication to the trier of fact and other legal actors has important implications for some of the most significant legal decisions, from pretrial detention to capital sentencing. Although considerable psycholegal research has focused on the process of risk assessment and management, a limited number of studies have examined how risk is communicated and interpreted by judges, juries, and other legal decision-makers as well as the public. This chapter examines the primary methods of risk communication and critiques their usefulness based upon the legal contexts in which they are most commonly offered. In particular, legal decisions based upon risk concerning pretrial release, sentencing determinations, and sexually violent predator (SVP) laws are highlighted to discuss more general issues with risk communication in the legal system. Suggestions for more effective and accurate presentation of risk are offered, as well as the practical and legal policy implications of adopting such practices.

This chapter describes the legal landscape related to Miranda rights and waivers, as well as the relevant research literature regarding Miranda waiver decisions. The chapter identifies factors related to Miranda rights comprehension and waiver and emphasizes research addressing interrogations of youth and their abilities to provide a valid waiver. Research has identified that suspect-related factors, including age, IQ, and psychosocial maturity, as well as structural factors, such as the length, reading level, and content of the Miranda warnings, are related to Miranda comprehension and waiver decisions. The chapter also discusses the legal standard for judicial decisions related to the admissibility of confessions following Miranda waivers, as well as the factors that judges typically consider when making such decisions. Because research demonstrates that many suspects struggle when making Miranda waiver decisions, we conclude by making policy recommendations and identifying areas in which future research is needed.

The prevalence of white-collar crime (WCC) is alarming. WCC has a significant negative impact on a country’s economy and overall society. Several social and personal factors have been proposed to explain why people make the decision to perpetrate WCC. This chapter presents a brief summary of the established risk factors, which explain the decision to commit white-collar crime. Further, the chapter explores affluenza as a potential predictor of the decision to commit white-collar crime. Affluenza is defined as entitlement driven by a deep value for one’s elevated socioeconomic status, which blinds people to the social consequences of their actions. We discuss how affluenza might contribute to a person’s decision to commit WCC, as well as its legal implications. Further, future directions for research investigating the role of affluenza in perpetration of white-collar crime are discussed.

Eyewitnesses play a significant role in criminal investigations and legal processes worldwide. Just like any other type of forensic evidence, eyewitness evidence has a margin of error. These errors, caused by numerous factors, affect the validity of eyewitness testimony. Some factors emerge at the moment of witnessing, while others occur afterwards. One of the main challenges for legal practitioners is to base their interviewing practices and decision-making on solid scientific evidence. Insight into the cognitive processes of a witness is vital for understanding why people make mistakes. Therefore, our chapter starts with a brief explanation of the organization of memory. Then, using a realistic example, we describe several variables that affect witness testimony, while loosely following the three stages of memory: witnessing, retention and retrieval. Next, we discuss various factors affecting judges’ and jurors’ assessments of witness testimony, which in turn influence legal decision-making. Finally, we summarize our findings and make some concluding remarks.

In Chapter 10 I present a Bayes net approach to modelling legal cases. I show how a small number of inference schemas can be used to capture a broad range of evidential issues. I suggest that this method could be used as a training tool to improve inferential reasoning in the legal domain.

Chapter 1 introduces the main questions to be tackled in the book, tracing a crime case from the discovery of a body to the verdict of a court. How do we generate initial hypotheses from sparse information? How do we develop our hypotheses as we gather new evidence? How do we make sense of a large body of conflicting evidence to reach a final decision? The crime case highlights the challenges we face: to explain what actually happened – the web of cause and effects that led to the death – but also to evaluate the evidence, assessing the many reports, claims and counterclaims. I argue that our minds are better prepared for explaining than evaluating.

Many countries around the globe rely on ordinary citizens, untrained in the law, to decide the guilt or innocence of their fellow citizens. Some countries use all-layperson juries, while others use mixed tribunals or mixed courts in which professional judges and lay citizens work together to decide a case. Still other countries use lay magistrates or lay judges working alone or on panels. This book provides a view of the different forms of lay participation and the ways in which they are evolving. It offers a comprehensive picture of how some countries have made recent and remarkable advances toward lay decision-making, while others have a long-standing form of lay participation that is well accepted in that country. Still other countries have faced challenges with lay participation and have opted for limiting the scope of lay legal decision-making or even abolishing it. The organization of this book illustrates that lay participation in a country is not fixed in stone; lay participation is being advanced, reinforced, or replaced in countries around the world. These shifting responses to lay participation suggest the prime importance of stepping back and taking a global perspective.