For more than 30 years, Darnell has been dedicated to supporting clients in areas such as strategy implementation, behavioral systems redesign and leadership development. Her expertise lies in coaching individuals and organizations toward effective behavior change. In January 2015, Dr. Lattal assumed the role of executive director of the Aubrey Daniels Institute after having served the last year as chair of Aubrey Daniels International's Board of Directors and serving 14 years as the firm's president and chief executive officer.

Outside the workplace, Darnell's professional contributions have included public school and university teaching, rural mental health practice, clinical private practice and working for the provost and president of a higher education institution. She has written several books on ethics and issues of management inside companies, including A Good Day's Work: Sustaining Ethical Behavior and Business Success (McGraw-Hill, 2007) and Workplace Ethics: Winning the Integrity Revolution (Rowman and Littlefield Publishers, 1993). She has served on the executive boards of two national groups dedicated to reducing violence in America. She continues to serve on numerous boards, publishes articles and blogs and is currently collaborating with Aubrey Daniels on a new book. Darnell's greatest joy is in furthering the incredible power for bringing out the best that behavior analysis provides to others, including to her seven grandchildren.

Darnell received her Ph.D. in 1980 in clinical psychology and behavioral systems from WVU and migrated steadily toward addressing systemic changes to influence behavior. She worked for consulting firms in Chicago and Pittsburgh before joining ADI in 1997 as head of strategic consulting. In 1999, she was appointed CEO and president. She credits the employees present and future at ADI for the continuing success of the company.