This white paper, prepared for the American University School of Public Affairs’ Justice Programs Office, is meant as a guide for lawyers representing clients with mental disabilities, especially in the context of drug courts. It argues that the task of improving the skills level of defense counsel in this representation of persons with mental disabilities in drug courts has to be approached simultaneously on two parallel, interlocking tracks:1. Education about mental disabilities and their impact on defendants in the criminal justice system, especially those in drug courts, and2. Education about those factors that contaminate the entire criminal justice process: sanism, pretextuality, heuristics, and the use of false “ordinary common sense”.Unless the second track is included, education – standing alone – is not a sufficient predicate for systemic meaningful change. In this paper, I discuss (1) the appalling statistics as to the percentage of persons in the criminal justice system who have a mental disability (including psychosocial disabilities [commonly referred to as “mental illness”] and intellectual disabilities [previously referred to as “mental retardation”]), (2) the key definitional criteria as to some of these disabilities, (3) some key factors to consider in how these disabilities are significantly different (although they are all too often commingled by judges, jurors and lawyers) from each other, and (4) some of the areas of criminal defense practice in which the presence of one of these disabilities is critically important. Lawyers must understand that a client’s mental health and cognitive impairment matter at every stage of the lawyer client relationship, from the first meeting to case strategizing to the plea/trial decision to the sentencing process and beyond, and must take seriously the full range of legal issues and behavioral issues that are presented. These issues include (1) the omnipresent “fear of faking” that plagues this system, (2) the impact of prescribed medications on client behavior and interaction with counsel, and (3) the likelihood of undiagnosed or misdiagnosed disabilities, I argue that it is critical that defense lawyers understand the differences between different disabilities, and how these differences may be critical in the representational process, whether the case involves the incompetency status, insanity defense, mitigation in a death penalty case, mitigation at sentencing, diversion to a problem-solving court, or, simply, as part of the entire “toolkit” that a lawyer brings to the representation of a “regular” criminal case in the context of plea negotiations or trial.