Maryland Attorney General Stephen H. Sachs asked the state's highest court today to send a convicted killer of a Garrett County deputy sheriff to the electric chair, arguing that those "called upon to protect public lives and safety must be specially insulated."

The man's lawyer said the facts in the case of Richard D. Tichnell, 33, of Fairmont, W.Va., fail to warrant Maryland's first execution in 19 years.

While Sachs contended that Tichnell "ambushed and coldly murdered" the deputy after robbing an Oakland Army and Navy Store last Jan. 18, attorney Clark B. Frame pleaded self-defense for his client and alleged "improprieties, inconsistencies and impuities" in the sentencing.

Tichnell is the first person sentenced to death under the capital punishment law enacted by Maryland in 1978 after prior laws were declared unconstitutional, and the judges of the Maryland Court of Appeals sought guidance during today's three hours of argument.

"We're sailing on uncharted seas," Sachs told them suggesting that they examine other cases in Maryland and in other states where murder of a police officer constitutes a special "aggravating circumstance" warranting the death penalty.

"What bothers me," said Associate Judge J. Dudley Digges of LaPlata, "is . . . what if we find similar situations where (the death penalty) was not imposed. What is our role?"

"You weigh that and you look at cases where it has been imposed," replied Sachs, citing two instances where Digges long ago had himself imposed the death penalty.

"I imposed them in different atmosphere, under different standards," said Digges.

"Some of these early cases may not have met these standards," added Chief Judge Robert C. Murphy.

The standards contained in the Maryland law that went into effect July 1, 1978, allow the death sentence if any one of 10 "aggravating circumstances," which must be proved beyond a reasonable doubt, outweigh any of seven "mitigating" factors in a murder case.

First, a defendant must be convicted of first-degree murder, and Tichnell's lawyer argued that the facts presented to a Wicomico County jury last summer failed to prove him guilty beyond a reasonable doubt.

Tichnell, a former Army paramedic irregularly employed since the steel plant at which he was employed closed rather than install environmental controls, first robbed the Oakland store of a single pistol last Jan. 5, Frame said. Three days later, he said, he returned with an accomplice and they stole nine more guns.

According to Tichnell, his accomplice went to look for a pistol that had been lost in the vicinity while Tichnell drove around the block. Returning, Tichnell said he said his accomplice under arrest and followed Deputy Sheriff David Livengood's instructions to lie down.

Then, Tichnell testified, Livengood's 108-pound dog Sarge attacked him, he ran to his car for a first aid kit and, with the deputy at close range firing at him, grabbed a semiautomatic pistol from the front seat and began shooting. He fired seven times, and then, Tichnell testified, he killed the dog with a Samuri sword.

Frame argues there was no premeditation in Tichnell's actions, which he said constituted self-defense. He said Tichnell deserves a new trial. The accomplice, who did not testify at Tichnell's trial, was separately tried and convicted of felony murder in January and sentenced to life in prison.

Sachs said the state's theory is that Tichnell had earlier loaded and cocked his pistol, intending to use it, and then "waited for the officer in a wooded area behind the store and gunned him down.

"No reading of the record can come to a conclusion other than that which supports the verdict," said Sachs. The shooting wasn't in self-defense, but came during Tichnell's "desperate flight" to avoid capture, said Assistant Attorney General Deborah K. Handel.

Frame contended that a "hostile atmosphere and climate" during the trial, which was moved from Western Maryland to the Eastern Shore to avoid such problems, prevented fair sentencing.

What he perceived as the jury's bias combined with the judge's remark in chambers that he wasn't sure this was "a death sentence case" led to Frame's decision to have the judge rather than the jurors impose the sentence. fFrame complained also that Circuit Court Judge Richard Pollitt allowed into evidence testimony about crimes for which Tichnell had been charged but not convicted.

Four of the seven appellate judges appeared to express concern over the sentencing proceedings that, if upheld, could cost Richard Tichnell his life. s