Despite an ostensible setback today, the Maryland General Assembly is expected to vote the state's gas chamber back into use this session.

The Senate Judicial Proceedings Committee voted 5 to 3 today to recommend disapproval of two bills to reinstate the death penalty in Maryland. The committee's action, however, is expected to be overturned later by the full Senate, just as in 1975, when the same committee's vote against capital punishment was overturned by the legislature.

While the committee has maintained a mojority of anticapital punishment senators, the vote tally in the full Senate does not appear to have changed since that body voted 25-to-22 in favor of a 1975 law mandating the death penalty for eight categories of murder.

The 1975 law was drawn in response to guidelines laid down by the Supreme Court. Last year, however, the Court re-examined the death penalty question and ruled that laws like Maryland's, which did not give judges and juries any choice about applying the penalty once the defendant was found guilty, of any of the eight murder categories, are unconstitutional.

As a result, Maryland legislators are now facing the death penalty question for the fourth time in as many years. In the House of Delegates, capital punishment has overwhelming support; and is expected to pass with little difficulty.

While the outcome in the Senate is not expected to change from 1975, the votes of some individual senators are. The spectacle of Gary Gilmore's execution in a Utah state prison last month crystalized a newfound opposition to the death penalty in one senator's mind, and strengthened the support for capital punishment in the mind of another.

The newspaper stories are still etched clearly in Sen. Thomas Patrick O'Reilly's mind: how Gilmore's body shuddered as five bullets tore into him, how the blood ran slowly down the execution chair, how the spectators went to peer with curiosity at the imprints of the bullets in the death chair.

"The description of how the blood was 'trickling down through the black . . .' - I can't remember what the language was," recalled O'Reilly, a Prince Georges County Democrat. "I guess it brought home to me the fact that we intentionally killed a person. And for what? What was gained?

"I'm glad he wasn't killed as a result of any bill I wrote or voted for," O'Reilly said.

In 1975, O'Reilly's first year in the legislature, he introduced a bill to make murders committed during tapes or kidnapings crimes punishable by death.Last week, he told a Senate committee he has changed his mind, that he now thinks capital punishment is "simply barbaric, unreasonable, a disgrace."

"I think I reasoned at the time that the bill was in defense of a third person (the victim), that rape and kidnaping were both what I considered crimes of specific intent" that the perpetrator had sat down and thought out before committing, O'Reilly said last week.

"Well, I think that's something that works well on paper, but life doesn't work that way.

"The individual who commits a murder does not sit down and reflect - I mean, it's logical, but that individual does not sit down in the middle of the crime and say, If I go farther, I'll get a more serious sentence.' They don't realize it," O'Reilly told the Senate Judicial Proceedings Committee last week.

The Gilmore case, with its massive publicity, its confusing legalities, and the absurdity of saving a man in order to kill him later, crystalized the opposition to the death penalty in O'Reilly's mind.The same spectacle had the opposite effect on Republican Sen. Howard Denis of Montgomery County.

"I still feel that the man may have been playing games with us, and that this may have been his bid for immortality," said Denis. "What I gathered from Gary Gilmore is that our system is in danger of being farcical, because defendants can string out the procedures almost forever."

Denis is a newcomer to the state Senote, appointed after the election last fall to replace former Sen. Newton I. Steers, who was elected to Congress. Steers voted against the death penalty in 1975, the last year Maryland enacted a sweeping death penalty statute; Denis' vote will be in favor of the death penalty proposal of this year.

"I don't think it's so much a matter of retribution as of the steps society can ask to defend itself," Denis said. "There are some people who commit the heinous crimes, who society should not suffer to live."