Undersheriff Williams began his career with the San Diego Sheriff's Office in 1992.   He was drawn to the supportive team environment, selfless professionalism, and the opportunity to have a challenging career with the department offering the greatest variety of assignments in the region.

During his career he served at multiple ranks in many areas of the department. He was assigned to Detention Services Bureau (El Cajon Jail, George Bailey Detention Facility, San Diego Central Jail, and Prisoner Transportation), Law Enforcement Services Bureau (Special Investigations Division, Sheriff's Homicide Unit, Criminal Intelligence Unit, Imperial Beach Substation, Lemon Grove Substation, Ramona Patrol Station, Rancho San Diego Patrol Station, San Marcos Patrol Station, Community Policing, and Valley Center Patrol Station), Court Services Bureau (Vista Court Services), and Human Resource Services (Personnel).

He promoted to Commander in 2021, and was assigned to Detention Services Bureau, where he oversaw Facilities and the Food Services Division.

In April 2022, he was promoted to Assistant Sheriff where he oversaw Court Services Bureau (Civil Division, Court Security, Extraditions, Field Services, Investigations, and Waterfront Park).  He also oversaw Human Resource Services Bureau (Background Investigations, Career Path, Detentions/Court Services Academy, Employee Relations, In-Service Training, Internal Affairs, Payroll, Professional Staff Training, Recruiting/Hiring, Regional Basic Academy, Risk Management, and Weapons Training).

In December 2022, Rich Williams was appointed to serve as Undersheriff where he is responsible for overseeing all department operations and ensuring the Sheriff's Office provides the highest quality public safety service to everyone in San Diego County. He is responsible for the department's $1.2 billion budget and more than 4,700 employees.  The employees of the San Diego County Sheriff's Office operate 19 patrol stations and substations, seven detentions facilities, seven Superior Court facilities and the related Civil Division, a nationally accredited Crime Laboratory, as well as regional investigative support, search and rescue, and tactical emergency response throughout San Diego County.

Undersheriff Williams is married with three children and possesses a Bachelor of Science in Criminal Justice degree from California Coast University.  He is a graduate of the POST Supervisory Leadership Institute, DEA Narcotics Unit Commander Academy, and the FBI National Academy, Session 272.