Meet Our Leadership Team
The MedMark Services leadership team consists of industry pioneers and experienced clinicians in the fields of primary care and addiction services. With a combined 115 years of experience, our team is committed to providing the highest quality care in an environment of dignity and respect.

	David K. White, Ph.D. President and CEO With more than two decades of health care administration experience in psychiatric care and substance abuse, physical rehabilitation, long term care and acute hospital services, Dr. David White joined MedMark as President and CEO in January of 2008.  Prior to joining the company, he served as President, Contract Management Services for Nashville-based Psychiatric Solutions, Inc.  Previously, he was President and Chief Operating Officer of Horizon Health Corporation, where he oversaw expansion and acquisition strategies, resulting in impressive growth.  He also served in a number of senior management roles during his twelve year tenure at Horizon.  Prior to Horizon, Dr. White was the CEO of Charles River Health Management, a psychiatric contract management company in Boston and Charles River Hospital, a specialty psychiatric and substance abuse hospital also in Massachusetts. He received a bachelor’s degree in science from Tufts University in Medford, Mass., and obtained master’s and doctoral degrees in clinical psychology from Vanderbilt University in Nashville.
	Michael G. Wallace Chief Financial Officer Michael G. Wallace joined MedMark as Chief Financial Officer in January 2008.  Mr. Wallace has 20 years of experience in health care finance, operations, business development, and consulting. He has led teams in a variety of health services venues, including ambulatory surgery centers, pharmaceutical services, physician practice management, and alternate site surgical services.  Prior to joining MedMark, Mr. Wallace was President and Chief Executive Officer of Genezen Healthcare, an office-based specialty biologics infusion services company.  Prior to that, Mr. Wallace was a senior healthcare consultant, filling interim Chief Financial Officer roles, leading post-merger integration teams, guiding companies through restructuring and providing leadership for start-up and early stage healthcare companies. Earlier in his career, Mr. Wallace served as Senior Vice President and Chief Financial Officer of Medical Alliance, Inc., a national, office-based surgical services company, playing an instrumental role in the company’s initial public offering in 1996.  Mr. Wallace holds a bachelor’s of business administration degree in accounting from Texas State University.
	Jeffrey A. Lempert, M.D. National Medical Director An experienced practitioner in the fields of internal medicine and primary health services, Dr. Jeffrey Lempert serves as National Medical Director for MedMark Services and has been with MedMark since 2003.  For more than thirty years, Dr. Lempert has contributed to the expansion and success of multi-specialty medical groups as well as primary care practices nationwide. He offers the unique combination of clinical knowledge and technological expertise.  Prior to joining MedMark, Dr. Lempert worked for more than 25 years as a member of the Mount Kisko Medical Group in Mount Kisko, New York, and was on the medical staff of the Northern Westchester Center in Westchester, New York. Dr. Lempert plays a critical role in MedMark's partnership with the U.S. Department of Veterans Affairs in leading the company's national community-based outpatient clinics. A graduate of Boston University School of Medicine, Dr. Lempert is board certified in internal medicine and completed post-graduate training at Boston University Medical Center. He has been recognized by the National Institutes of Health and holds medical licensure in New York, Florida, California, Indiana, Georgia, New Hampshire and Massachusetts.
	Raymond N. Dattoli Director of Human Resources With more than 25 years of experience, Mr. Dattoli leads the MedMark Services human resources team. He has served in senior-level positions with internationally recognized organizations such as General Electric Corporation and Schneider Corporation’s Square D Group. Mr. Dattoli shares the MedMark commitment in his innovative and energetic approach to recruiting, retaining and developing the nation’s best employees.  A Chicago native, Mr. Dattoli is an honors graduate of the prestigious St. Ignatius College Preparatory School and holds bachelor’s degree in psychology from Loyola University. Mr. Dattoli remains active in community affairs by coaching youth football and speaking at various venues on topics such as building and preserving a team-orientated workforce.
	Nicole A. Jernigan Director of Operations / Addiction Services Nicole Jernigan joined MedMark Treatment Centers in October 2006 as Coordinator of Quality Assurance and Performance Improvement. In August 2007, she was promoted to the position of Director of Operations. She came to MedMark from PharmaTox Partners, a non-profit organization providing training and technical assistance to substance abuse treatment providers serving the Latino population. There she also served in various roles, including Associate Director for the Institute of Addiction Studies, Executive Administrator for the company’s residential and outpatient drug treatment programs and Director of Quality Assurance and Improvement. In addition to her current role, Ms. Jernigan also serves as an administrative surveyor, conducting national quality surveys and providing consulting services on behalf of the Commission on Accreditation of Rehabilitation Facilities. Ms. Jernigan obtained a bachelor’s degree in liberal studies from California State University in Dominguez Hills in 1999. She is currently pursuing a master’s degree in public health from Benedictine University in Chicago.
	Tracy S. Sims, M.A. Director of Veteran’s Affairs Operations Mrs. Sims brings more than 17 years of clinical experience to her position as Director of Veteran’s Affairs Operations with MedMark Services.  An experienced professional, she previously served as a National Clinic Specialist for Sterling Medical Corporation where she oversaw the operations of their community-based outpatient clinics dedicated exclusively to serving our nation’s veterans. Tracy is a certified medical assistant and a graduate of Webster College. She is active in numerous civic and charitable organizations, having served the Girl Scouts of America and various veterans’ organizations for more than 17 years.