Lieutenant Colonel Giannini was born in California and attended college at California State University Sacramento. He went through Platoon Leaders Course at Quantico, Va. in 2003 and 2004. He graduated from college in 2005 with a Bachelor of Science in Criminal Justice and commissioned as a 2nd Lieutenant in the United States Marine Corps. Upon completion of The Basic School and Military Police School, Lieutenant Colonel Giannini reported to Marine Wing Support Squadron 271 at Cherry Point. He deployed to Iraq in support of Operation IRAQI FREEDOM in 2007 where he served as the Incident Response Platoon Commander. Upon return, he served as the Anti-Terrorism Officer for II MAW. In 2008, Lieutenant Colonel Giannini deployed back to Iraq with 1st BN 12th Marines as a Platoon Commander.

In 2009, Lieutenant Colonel Giannini left active duty and entered the Reserves. He reported to 23d Marine Infantry Regiment in San Bruno, CA. He served as a Civil Affairs Officer and Anti-Terrorism Officer. Subsequently, he served as the H&S Company Commander. In 2011, he deployed to the Kingdom of Bahrain with Marine Central Command Forward (MARCENT FWD) as the Anti-Terrorism and Training Officer. In 2013, Lieutenant Colonel Giannini deployed to Afghanistan in support of Operation ENDURING FREEDOM as a security forces assistance advisor to the Afghan National Army. Upon return, Lieutenant Colonel Giannini reported to I MEF G3/5 and served as an action officer and Defense Readiness Reporting Officer.

In 2019, Lieutenant Colonel Giannini deployed to Iraq in support of Operation INHERENT RESOLVE as an Acquisitions Officer in the Directorate of Military Assistance. In 2022, he arrived in the Republic of Korea to serve as Camp Mujuk’s Executive Officer.

Lieutenant Colonel Giannini serves as a Sergeant in the Contra Costa County Office of the Sheriff. He is a Supervisor and Team Leader for the Special Weapons and Tactics and Designated Marksman Teams.  

Lieutenant Colonel Giannini holds a Masters of Science degree in Criminal Justice from the University of Cincinnati and is a graduate of Marine Corps Command and Staff College. His personal decorations include the Joint Service Commendation Medal, Navy and Marine Corps Commendation (x2), Navy and Marine Corps Achievement Medal (x2) and Combat Action Ribbon.