LtCol Newkirk was raised in Utah, Arizona, Alaska, and California, graduating from Soquel High School in Santa Cruz, California in 1997. LtCol Newkirk enlisted in the Marine Corps Reserve in 1997, joining 2nd Battalion, 23rd Marines as a Rifleman in January 1998. Subsequently serving as a Rifleman, a Motor Transport Operator and Air Support Operator at various units for the next six years. Sergeant Newkirk was activated in June 2004 with Marine Air Support Squadron-6 and deployed to Iraq and Qatar in support of Operation Iraqi Freedom-II, where he served as a Marine Liaison Officer with the Air Force's Joint Surveillance Target Attack Radar System (JSTARS) and as a Senior Air Director at Camp Al Quim in Western Al Anbar.

During his deployment for OIF, Sergeant Newkirk was selected for the Reserve Enlisted Commissioning Program (RECP) and reported to Officer Candidate School in Quantico, VA in January 2005. Commissioned on 25 March 2005, Second Lieutenant Newkirk completed training as an Infantry Officer and attended LAR Leaders Course before joining Co B, 4th LAR as a Platoon Commander in February 2006. In June 2006, Second Lieutenant Newkirk was mobilized with Company B, participated in pre-deployment training in Camp Lejeune to qualify the unit as a Provisional Small Craft Company, and deployed to Hadithah, Iraq as a Platoon Commander in October 2006. Second Lieutenant Newkirk was promoted to First Lieutenant in March 2007 and returned from Iraq in May 2007, demobilizing the following month.

For the next two years, Lieutenant Newkirk drilled as a Platoon Commander and Company Executive Officer and was promoted to Captain in May 2009. Shortly thereafter, in June 2009, Company B was again mobilized for combat operations in Afghanistan and deployed to the southern Helmand Province from October 2009 to May 2010. Following redeployment, Captain Newkirk attended Expeditionary Warfare School as resident student in Quantico VA, graduating in June 2011. Captain Newkirk then joined 4th Air and Naval Gunfire Liaison Company (4th ANGLICO) in West Palm Beach, FL where he served as a Firepower Control Team (FCT) Leader and Joint Terminal Attack Controller (JTAC).

In September 2012, Captain Newkirk assumed command of Company B, 4th LAR and served as the Company Commander through to September 2014. Captain Newkirk then served as the Assistant Operations Officer for 4th LAR at Camp Pendleton, CA from September 2014 to July 2015 and was promoted to Major on 1 May 2015. In July 2015, Major Newkirk reported to the Army's Command and General Staff College in Fort Leavenworth, KS and following graduation in June 2016, reported to 3rd Battalion, 25th Marines where he served as the Battalion Operations Officer and Battalion Executive Officer from June 2016 to Sep 2019. Concurrent with a period of his reserve duty at 3/25, Major Newkirk served on active duty from July 2017 to Sep 2018 as the Senior Watch Officer at the Marine Corps Operations Center (MCOC) in the Pentagon, D.C. Following his tour at 3/25, Major Newkirk served as an
Individual Mobilization Augmentee (IMA) with the Marine Corps Operations Center from Sep 2019 to Dec 2020. Major Newkirk then joined the US AFRICA Command IMA detachment and after being promoted to LtCol in May 2021, accepted active duty orders and served as the Branch Chief, Current Operations, Information and Cyber Operations Division, United States Africa Command. After completing ADOS orders, LtCol Newkirk returned to the AFRICOM IMA det and has been serving as an Information Operations Planner in the Info and Cyber Division since Nov 2021. LtCol Newkirk assumed command of 4th Light Armored Reconnaissance Battalion on July 16, 2022.

LtCol Newkirk's personal decorations include the Meritorious Service Medal, Air Medal Strike/Flight w/ numeral “5”, Joint Service Commendation Medal, Navy and Marine Corps Commendation Medal with Gold Star, Navy and Marine Corps Achievement Medal w/ combat “V” and two Gold Stars, and the Combat Action Ribbon.

LtCol Newkirk's civilian career has been primarily in the airline industry, and he is currently flying and teaching as a Boeing 757/767 Instructor Pilot for United Airlines based in Denver, CO.