En route to passing a bill that would re-institute the death penalty in Maryland, the state Senate today encountered its first filibuster of this year's session as a black senator from Baltimore undertook a one-man talkathon.

When the green lights on the Senate's overhead voting machines indicated a vote on the death penalty bill was imminent, Sen. Clarence M. Mitchell III (D-Baltimore) stood up and told his colleagues they might as well go home.

"The committees can conduct their voting sessions (the Senate's main task on Fridays is to vote on bills in committee), and leave the floor," said Mitchell, because whenever they get back, "I'll still be talking."

Mitchell was true to his word. In an unlikely attempt to hold off the Senate's almost certain approval of the bill to re-institute the death penalty in Maryland, Mitchell began the first of what could be several filibusters in the Senate this session.

Into the day and evening, Mitchell, who is immensely popular in his inner-city Baltimore district, read statistics on the death penalty, the names of the 79 people executed in Maryland between 1923 and 1961, and a long, detailed study that used a mathematical regression analysis to conclude that capital punishment is not a deterrent to murders.

"I feel as strongly about this piece of fraud (the death penalty bill) as the sponsor (Baltimore County Democrat Sen. John C. Coolahan) felt about the rapid transit bill," said Mitchell, in reference to Coolahan's leadership of a filibuster during last year's session of a proposal to build a subway in Baltimore.

"There are those who suggest that the death penalty is not an issye along racial lines," said Mitchell, in one of many references to his main reason for opposing the bill.

"The concept of it perhaps is not. But the practice of it is."

Mitchell said 79 persons were executied in Maryland between 1923 and 1961, the last year anyone suffered death at the hands of the state. Of them, he said, 62, or 79 per cent, wer black, while blacks comprised about 18 per cent of the state's population.

The likelihood of Mitchell's avoiding Senate passage of the death penalty bill is minimal. THere are 45 days left in the 90-day legislative session, and Mitchell would have to consume most of them before Senate leaders gave any serious thought to derailing the death penalty proposal.

It is unclear how many other senators will join Mitchell in his filibuster. Sen. Verda Welcome (D-Baltimore), another black senator, spoke for about in hour this afternoon, but said she is not part of any organized effort to filibuster the bill.

Sen. Robert L. Douglas (D-Baltimore), chairman of the legislature's black caucus, said the caucus has taken no position on filibustering the death penalty. "It was his (Mitchell's) decision." said Douglas.

Even if Mitchell fails, and the Senate approves the death penalty, the bill would not safe from filibusters, however. After it leaves the Senate, it will go to the House, where easy approval is expected.

But the Senate bill includes an amendment that Coolahan vehemently opposed on the Senate floor, and has indicated he will try to have removed in the House. The amendment requires that a jury vote on a death sentence be unanimous, rather than a simple majority as the bill originally specified.

If the House acquiesces in removing the amendment, the bill will come back to the Senate for approval in its newly-amended version. If the bill returns to the Senate near the April 11 closing date for the session, a new filibuster, with a far shorter time period to span, would pose a more serious threat to the bill.

At least one black senator, Sen. Tommie Broadwater (D-Prince George's) , said today he plans to filibuster the bill if it comesback from the House later in the session.

Coolahan said he is now unsure whether he will try to have the amendment removed in the House. "I have to determine a time factor," he said. "We can't have it come back here in the last five days, the bill will he killed."

But for the moment, Coolahan said with a smile, "Let him talk . . . He can go home and tell his black brethren in his district he' saved them from the cynaide pill."