New insights into the neural processes that underlie cognition and behaviour have led to discussions about the relevance of these discoveries for the criminal justice system. Conversely, laws can influence the direction of neuroscience research. These issues have led to the emergence of, for example, several interdisciplinary 'Neuroscience and Law' initiatives in the United States and a recent report on the topic by the Royal Society in the United Kingdom. In this issue of Nature Reviews Neuroscience, we launch a series of Perspectives articles that explore the interactions between neuroscience and the law.

New technologies, in particular functional MRI, are beginning to reveal which brain areas and networks regulate particular behaviours and decisions, and studies have shown that certain factors, such as psychiatric disorders, affect decision-making processes. But does this mean that activity in these areas can predict with any certainty a person's behaviour or tell us whether someone is speaking the truth or telling a lie? And does the presence of such factors necessarily decrease a person's culpability in a criminal act? Neuroscientists are responsible for explaining the limitations of these technologies and the difficulties in interpreting the data they generate, especially when acting as expert witnesses in court.

Studies in animals and humans have revealed the mechanisms involved in memory formation, consolidation, reconsolidation and retrieval, and it is now well known that memories can be malleable and change over time. This has implications for the interpretation of memories of not only eye witnesses but also jurors and judges, who have to remember large amounts of information when making life-changing decisions about other individuals.

The interaction between law and neuroscience is bidirectional. One example of laws influencing neuroscience pertains to national and international regulations that make it difficult to obtain licences to investigate psychoactive drugs. This has greatly restricted research into both the potentially therapeutic actions and the potentially harmful effects of these drugs. Another example is provided by policies regarding the creation of human embryonic stem cell lines for research purposes that may limit the availability of these resources for neuroscientific research.

These are some of the issues that will be explored in the article series. We begin the series with a Science and Society article by Laurence Steinberg (page 513) that considers how neuroscience has contributed to US Supreme Court decisions about the criminal culpability of adolescents.