Both a sheriff and a constable are tasked with maintaining peace and arresting criminals, but a constable is elected to serve a municipality, while a sheriff is elected to serve the county, states the Legal Dictionary of the Free Dictionary. A constable must defer to the authority of a sheriff.
Constables and sheriffs may be called upon to function as a process server for the area courts, notes the Legal Dictionary of the Free Dictionary. They also may be called upon to monitor the custody of juries, attend criminal court sessions and process the service of writs. Both offices are often tasked with the seizure and management of property as ordered by the courts. The offices are responsible for auctioning off the seized property and distributing the fund per the instructions of the court order.
One unique power possessed by the sheriff is the ability to form a posse, reports the Legal Dictionary of the Free Dictionary. The power dates back to the common-law duties of the English. A posse creates a group tasked with the immediate assistance and aid to a sheriff in need. A posse is typically a short term solution to a specific issue that poses imminent danger.