About Sean M. O'Neill
Partner
Legal Experience
Military Service

I was born and raised in Fremont, California and attended Mission San Jose High School where I graduated in 2000. When I turned 17, I enlisted in the United States Marine Corps and was trained as an infantryman or, as commonly called in the Marines, a grunt. During my time in the Marines I was stationed at Camp Pendleton in San Diego and went on three deployments.
In 2002, I deployed with a Marine Expeditionary Unit, traveling to Singapore, Jordan, Kuwait, Bahrain, and Australia. In 2003, I was in initial wave of the invasion of Iraq with the First Light Armored Reconnaissance Battalion of the First Marine Division. In 2004, I returned to Iraq where I was wounded in an ambush on the Iraqi-Syrian border in the town of Al-Qaim. In April of that year I participated in the First Battle of Fallujah, following which I received a Navy Achievement Medal for valor and a Purple Heart.
During my final deployment, I rose to command my own vehicle and 6 other Marines in various combat operations in Al-Anbar Province in Western Iraq.
In 2002, I deployed with a Marine Expeditionary Unit, traveling to Singapore, Jordan, Kuwait, Bahrain, and Australia. In 2003, I was in initial wave of the invasion of Iraq with the First Light Armored Reconnaissance Battalion of the First Marine Division. In 2004, I returned to Iraq where I was wounded in an ambush on the Iraqi-Syrian border in the town of Al-Qaim. In April of that year I participated in the First Battle of Fallujah, following which I received a Navy Achievement Medal for valor and a Purple Heart.
During my final deployment, I rose to command my own vehicle and 6 other Marines in various combat operations in Al-Anbar Province in Western Iraq.
Education

In September of 2004, I left the Marines and began my college studies, ultimately graduating from UC Berkeley in 2008. During my time at Cal I realized that my passion lay in the law and its power to protect and preserve the rights of all individuals in our society. Following my graduation from Cal, I began my legal studies at Santa Clara University’s School of Law, with a focus on tax and employment law.
While in Law School, I honed my courtroom skills via a clerkship with the Santa Clara County District Attorney’s Office where I successfully litigated Penal Code § 1538.5 hearings, which are motions by defendants to suppress evidence.
While in Law School, I honed my courtroom skills via a clerkship with the Santa Clara County District Attorney’s Office where I successfully litigated Penal Code § 1538.5 hearings, which are motions by defendants to suppress evidence.