Marshall was born and raised in Lake City, Florida and attend Columbia High School.
As a junior, Marshall earned first-team All-State honors and was considered to be "among the best safety prospects in the nation.
[5] Marshall attended Florida State University beginning in January 2014 as an early enrollee, and he played four seasons with the Seminoles, appearing in 31 games.
Despite losing 50 pounds due to his stomach injury, Marshall was able to work his way back to shape and play as a true freshman, appearing mostly on special teams.
[8] Marshall was promoted to the active roster on December 10, 2018 in order to prevent him from being signed by the Arizona Cardinals, releasing special teams regular Shamarko Thomas in the process.