Vice Admiral MacDonald graduated from the College of the Holy Cross in 1978 with a Bachelor of Arts degree in English, and entered the Navy in May of that year.

VADM MacDonald was commissioned an ensign in the unrestricted line through the Naval Reserve Officer Training Corps.

Following the normal Surface Warfare pipeline, he reported to the USS Hepburn (FF 1055) in October 1979 where he served as Main Propulsion Assistant and Navigator.

Carol Rosenberg, of the Miami Herald, reports that MacDonald had testified before the United States Congress on numerous occasions, defending the Guantanamo Military Commission system.

[5] MacDonald testified on February 13, 2013, at the military commission of Khalid Sheikh Mohammed, and the four men accused of being his co-conspirators.

[8][9][10] Defense attorneys had argued that MacDonald had improperly approved death sentences prior to their clients being provided with informed legal advice.