The Chester's Mill Sheriff's Department is a law enforcement agency operating in Chester's Mill. The department was headed by Sheriff 'Duke' Perkins, from the Town Hall. The department is believed to have many Deputies employed, however, on the day the dome came down, many of them were at a Parade in Westlake, and were left on the outside, as a result the Department resources are spread thin.
The Department has struggled to maintain control within Chester's Mill due to inexperienced leadership after the demise of Sheriff Perkins, the manipulation of Second Councilman 'Big Jim'Rennie and lack of proper officers to maintain the peace.
- Sheriff Duke 'Howard' Perkins (Deceased) - The experienced Sheriff of Chesters Mill. Confident and assertive. The last significant opposition to Second Councilman 'Big Jim' Rennie. He died when he touched the Dome which subsequently exploded his pacemaker in his chest, killing him instantly.
- Sheriff Linda Esquivel (Deceased) - Promoted to Sheriff by 'Big Jim' and tasked with restoring some sort of sembelance and order within Chester's Mill. She had to deal with the aftermath of the Dome's arrival and the lawlessness it created. Heavily manipulated by 'Big Jim' and had to rely on 'Special Deputies' after the death of Deputy Denton and Randolph. Her death was the end of the Chester's Mill Sheriff Department's official officers.
- Sheriff Phil Bushey (Deceased) - The former Sheriff of Chester's Mill who lacks knowledge and experience of law enforcement. Promoted by 'Big Jim'. He is killed when he gets impaled by a stalagmite.
- Sheriff Dale Barbara - The Current Sheriff of Chester's Mill who was previously in the army.
- Sheriff James Rennie Sr. - The Current Sheriff of Chester's Mill who was previously the councilman.
Sheriff Duke Perkins was against the suggestion by Second Councilman 'Big Jim' Rennie that Councilman have the power to authorize additional police officers during emergencies and claimed "The last thing this mess needs is amatures with badges". And Duke states till he hears from the Mayor or above, 'Big Jim' is not authorising anything.
Yet with the death of Sheriff Perkins and Deputy's Denton and Randolph, newly promoted Sheriff, Linda Esquivel is forced to hire replacement Deputies from those inside the Dome.
With the death of Sheriff Perkins, Deputy Randolph begins to panic which eventually led to him opening fire with his pistol at the Dome. The bullet ricocheted and ended up hitting Deputy Denton, killing him instantly. When Randolph escaped police custody, he was eventually shot and killed by Deputy Esquivel.
Under the Dome
The structure of the Sheriff's Department on the day the Dome came down was:
- Sheriff Howard 'Duke' Perkins
- Deputy Linda Esquivel, Dukes second.
- Deputy Freddy Denton
- Deputy Paul Randolph
The series starts with the Department already being understaffed due to half of the department being trapped outside the Dome. Sheriff Howard 'Duke' Perkins is a confident and able Sheriff of the Town who is shown to do whatever's necessary to protect the Town of Chester's Mill. When the Dome comes down, Sheriff Perkins is informed by Deputy's Denton and Randoplh of downed power lines by the Clinic and Food Mart. Sheriff Perkins and Deputy Linda Esquivel then become the first responders inside the Dome to investigate the 'Plane crash'.
Upon arrival, Perkins is cautious of the 'Dome' and urges Deputy Esquivel to step away as he then begins to organise the operation of shutting down all the roads leading outside the Town.
Season Two 
Season Three 
The Sheriff's Department has a wide arsenal of weapons available to them when the Dome comes down. Riot Gear was sent to the department by the Federal Buearu of Investigation after the 9/11 attacks. This included Tear Gas which has since lost it's effectiveness.
- Sheriff Linda Esquivel reveals two rules of Law enforcement that Duke taught her on the first day of the job.
- Rule number one: Always believe in the goodness of the people you serve.
- Rule number two: Do what you've got to do.
- Strangely several of the hired police officers and replacement sherrifs have been some of the more mentally unstable or immoral residents.
- Big Jim, Sherrif - Part of a drug manufacturing group, murdered; Lester, Agatha and Maxine Seagrave, Otto, Boomer, Dodee, Lyle, Rebecca, Andrea and Marston, tried to frame Barbie for several of these murders.
- Phil Bushey, Sheriff - Assaulted Big Jim and attempted to kill him, killed Wendell, blew up a large building injuring many residents, attacked Carolyn and held her hostage.
- Paul Randolph, Deputy - Assaulted Linda, accidently shot and killed Freddy, shot Rodger.
- Junior Rennie, Deputy - Attacked Angie and locked her in a fallout shelter, murdered Clint Dundee, assaulted Barbie.
- Carter Thibodeau, Deputy - Bullied Joe McAlister, tried to make a monopoly, charging people to use Joe's generator.