Following a 3-day series of presentations on psychopathy that I delivered in Australia some 20 years ago, a criminal defence lawyer took the podium and said, Sitting beside me is a dangerous man. After looking around to find this man, I realised that he was talking about me, as the developer of the Psychopathy Checklist- Revised (PCL-R; Hare, 1991, 2003), which he saw as a powerful tool capable of misuse and abuse. Prior to these comments, a prominent consultant psychiatrist said to the audience, Some but what do they mean? These were early brain images my colleagues and I had obtained from psychopathic and other individuals while they processed semantic and emotional material (later published as Intrator et al., 1997; Kiehl et al., 2001). As it turns out, the lawyer was correct in one respect; the PCL-R can and has been misused, but his characterization of me as a dangerous man seemed to conflate the creator of a tool with the ways in which it is used. The psychiatrist technically was correct at the time, but the few imaging studies then available have grown to several hundred, conducted by scores of researchers from around the world. Nonetheless, problems in interpreting neuroimages remain, most seriously in the legal system.Since my Australian experience the number of articles on the PCL-R and its derivatives has increased at an exponential rate, from less than 50 in 1995 to more than 1,100 by the time of this writing (Web of Science, October, 2015). These articles reflect, among other things, investigations and commentaries in two broad areas: basic theory and research on the nature and measurement of psychopathy (e.g., see Patrick, in press); and applications to the mental health and criminal justice systems (e.g., see Gacono, 2016). My web page (www.hare.org) contains a detailed and up-to-date list of articles on these and other issues.In this article, I address the criminal lawyer's concerns by outlining some of the advances in measuring and understanding psychopathy, and by discussing some current issues and debates in the legal system about the use of the PCL-R and the construct it measures. The psychiatrist's early concern about the use of pretty pictures in the study of psychopathy is echoed in current research on psychopathy and in the recent applications of neuroscience in the legal system (neurolaw) to determine criminal culpability (Lushing, Gaudet, & Kiehl, 2016). Because of space limitations, I will not discuss these latter issues, but will offer only a few comments.In the foreword to The Handbook on Psychopathy and Law (Kiehl & Sinnott-Armstrong, 2013), I had this to say,There is little doubt that many psychopathic features are associated, in theoretically relevant ways, with a variety of brain structures and functions that differ from those of the majority of other individuals. But, this does not necessarily mean that they suffer from a neurological deficit or dysfunction...weshould consider the possibility that the actions of psychopaths reflect cognitive, affective, and behavioural processes and strategies that are different from those of other people, but for reasons other than neuropathology or deficit, in the traditional medical and psychiatric sense of the terms. (Hare, 2013, pp. vii-ix).One viable possibility is that psychopathy is an evolutionary adaptive life-strategy rather than a disorder (e.g., Book, & Quinsey, 2003; Glenn & Raine, 2014; Lalumiere, Mishra, & Harris, 2008; Mealey, 1995). Further, with respect to neurolaw, how different from do brain structure and function, and cognitive, affective, and behavioural processes, need to be in order to be considered abnormal or deviant for legal purposes, including determinations of culpability? At present, we lack baselines for normal brain function from the general population during the tasks used to study psychopathy. Recent discussions of these and related issues are covered extensively in several recent articles and chapters (e. …