Began his 27 year career in 1995, as a cadet at the 23^rd Corrections Academy. After graduation, he was assigned to the Detention Services Bureau where he worked at the Old San Diego Central Jail, and George Bailey Detention Facility.

He then attended the 35^th Law Enforcement Academy in 1996.  He began his first patrol assignment serving the community of Encinitas.  Assistant Sheriff Nevins spent 16 years at the rank of Deputy Sheriff working at Lemon Grove Patrol Station, Special Enforcement Detail, and In-Service Training Unit. 

As a Sergeant, Lieutenant and Captain, he was assigned to Law Enforcement Services Bureau (Lemon Grove Substation, Lakeside Substation, Rancho San Diego Patrol Station, Special Enforcement Detail, and Criminal Intelligence Unit), Human Resource Services Bureau (In-Service Training Unit, Weapons Training Unit, and Internal Affairs), and Court Services Bureau (Chula Vista Court, El Cajon Court, Juvenile Court, and Kearny Mesa Court).

He promoted to the rank of Commander in April 2022, where he oversaw Law Enforcement Services Bureau – Patrol (San Marcos Station, Valley Center/Pauma Substation, Vista Station, Fallbrook Substation, Poway Station, 4S Ranch Substation, Ramona Substation, Rancho San Diego Station, Lemon Grove Substation, Imperial Beach Substation, North Coastal Station, Santee Station, Lakeside Substation, Alpine Station, Ranchita/Warner Springs, Campo/Tecate, Julian Substation, Pine Valley Substation).

In 2023, he promoted to Assistant Sheriff where he manages Court Services Bureau (Civil Division, Court Security, Extraditions, Field Services, Investigations, and Waterfront Park).  He also oversees 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/Medical Liaison, and Weapons Training).

Brian was raised in East County and graduated from Valhalla High School. He is an FBI National Academy Graduate and holds a degree in Criminal Justice Management.