Born overseas into a military family, Justice McDonald was raised in Des Moines. He earned his undergraduate degree from Grand View University in 1997, and he earned his law degree from the University of Iowa in 2001. Justice McDonald graduated from law school with highest distinction. He received the John F. Murray Award and earned Order of the Coif Honor Society recognition.
After graduating from law school, Justice McDonald served as a law clerk to the Honorable David R. Hansen, United States Court of Appeals for the Eighth Circuit. Justice McDonald then worked in private practice in Central Iowa for a number of years before being appointed to serve as a Judge of the District Court, Fifth Judicial District of Iowa. In 2013, he was appointed to the Iowa Court of Appeals. In 2019, he was appointed to the Supreme Court of Iowa.
Justice McDonald has been an active member of his community. He has supported numerous non-profit, community, and professional organizations in Iowa. He has served on the Board of Directors of Bravo Greater Des Moines, the Iowa Asian Alliance, the Iowa Foundation for Microenterprise and Community Vitality, and the Iowa Judges Association, among others. Justice McDonald is a recipient of the Governor's Volunteer Award.
Justice McDonald is married and has three children.