Charles County Sheriff David D. Fuller, 45, citing job stress and county politics, has announced that he is retiring, a year before his four-year term expires.

Fuller, who has overseen the 100-deputy department since his election in 1978, said he plans to trade in his badge for a fishing pole and move to a second home in Garrett County.

Fuller announced his intention to resign earlier this month in a letter to Gov. Harry Hughes, who must appoint an interim successor until elections are held in November 1986.

But Fuller did not say when he would leave office, prompting the governor's appointment officer, Connie Beams, to say, "Without a specific date there can be no real vacancy."

Fuller, who has been staying at his home in Garrett County, did not return a reporter's calls last week about his resignation. In his absence, Fuller has delegated leadership to Maj. Ross Pitrelli.

During the past two years, Fuller's term has been marked by frequent absences and by controversy, culminating in a public tongue-lashing in April by a Circuit Court judge during a county-wide gambling probe.

Fuller testified for the defense during the trial of County Commissioner Marland Deen, who was convicted of one count of paying off winners on an illegal video poker machine.

In his testimony, Fuller said that the county's gambling laws were "confusing" and that they were being selectively enforced for political reasons by the state's attorney.

Judge C. Clarke Raley disagreed. He sentenced Deen to 60 days in jail, saying there was collusion among elected county officials on the issue of illegal gambling.

"You finally get a situation where a sheriff takes the stand and tells the citizens, 'I am greatly confused.' No law enforcement chief has the audacity or the right to say he's confused. He has 80,000 people depending on him," Raley said at the trial.

Last week Raley said Fuller's resignation "proves that I was right and the jury was right in the first place. His leaving completes the catharsis the county needed . . . . "

Russell Levin, a member of the Republican Central Committee, defended Fuller, a lifetime county resident, saying Fuller had assumed office at a "difficult time for anyone, a time of tremendous growth, and he developed the department into a very efficient law enforcement agency."

Levin said Fuller's biggest mistake may have been an "inability to realize that elective office does involve politics . . . . "

State Sen. James C. Simpson (D-Charles, St. Mary's) said the sheriff's department has suffered from Fuller's "absentee management" for nearly two years and is "like a ship without a captain." Simpson said several deputies have come to him complaining of low morale and favoritism in the hiring and promotion practices followed by Fuller.

Former State's Attorney Stephen Braun, who had earlier called on Fuller to resign, said selection of his successor is "crucial" to Charles County.

"Basically, the department has been without leadership for about two years. He's not been giving law enforcement his full-time attention," Braun said. Braun and others said Fuller divided his time between his police job and a video store that he and his wife owned until last week.

Braun said, "A lot depends on the governor's appointment. Charles County is not like other jurisdictions where the sheriff's department usually takes care of transporting prisoners and serving warrants. This is our main law enforcement branch."