Dorsey, 63, was convicted last month of ordering the murder of Derwin Brown, who was shot and killed Dec. 15, 2000, three days before he was to take office after beating Dorsey in a bitter runoff election.
Dorsey, who also was found guilty on 11 of 14 charges of corruption in the sheriff's department, may one day be eligible for parole.
``Words cannot express the magnitude of this case, and hopefully there will never be another,'' District Attorney J. Tom Morgan said after the hearing.
``A sworn official, an elected official, used the power of his position to order the assassination of another elected official. This community has suffered because of this crime.''
But at his sentencing hearing, Dorsey maintained his innocence in both the murder and charges of corruption.
``I know you're going to sentence me severely, but I do not have the blood of Derwin Brown on my hands,'' Dorsey told Judge Cynthia Becker. ``I'm going to be in prison on the outside, but I'll be free on the inside because I do not have the blood of the sheriff-elect on my hands.''
He insisted:
``I was not a party to the murder of Derwin Brown. I did not orchestrate it, I did not plan it, I did not play a role in the diabolical and horrible murder of the sheriff-elect. However, here I am.''
Prosecutor John Petrey asked Dorsey whether he regretted any corruption or theft that occurred while he was sheriff.
``I have never considered anything I did as theft,'' Dorsey replied.
Brown's mother, Burkena Brown, one of five family members who spoke on Brown's behalf at the hearing, told the court: ``There is a hole where my heart used to be.''
Prosecutors charged that Dorsey recruited men to kill Brown, 46, so he could retake the sheriff's post in a special election. As rumors swirled of his involvement in Brown's slaying, Dorsey decided not to run.
The murder case was based chiefly on the testimony of two men, Patrick Cuffy and Paul Skyers, who said they helped carry out the slaying. Both men struck immunity deals with prosecutors.
Two other men, Melvin Walker and David Ramsey, were acquitted of murder charges in a separate trial.
Dorsey will serve his sentence in a prison in the Atlanta area, but the exact location was not disclosed.