In a courtroom in southeast Moscow today, the Kremlin is scheduled to begin the trial of a man who sought to test the Soviet Union's international pledges to uphold human freedoms in its own country. For many in the Western community here, a guilty verdict is a foregone conclusion.

The trial of Yurt Orlov and those expected shortly of his colleagues Alexander Ginzburg and Anatoli Scharansky, as well as trial of their colleagues in other cities, will stand as a clear test of the reality of the Kremlin's human rigths guarantees.

For the Kremlin, the stakes are great: the leadership is trying to wrap itself in the cloak of legality in its uneven match with the dissidents to muffle Western criticism and maintain its claim of moral righteousness before Communist parties in other nations.

Soviet leader Leonid Brezhnev has heatedly denounced the West's support for the dissidents as "internal meddling" in this country's private dealings with its own citizens. Soviet spokesmen at such forums as the recent Belgrade conference on the Helsinki accords have maintained that the Western democracies in general and the United States in particular, are guilty of grave human rigths abuses of their own that mock Western outcries on behalf of the dissidents.

President Carter has made human freedoms in other countries a major ingredient of his foreign policy, speaking our often against the repression of the dissidents here and elsewhere.

But early in his administration, after a series of sharp clashes with the Soviets, Carter toned down his public gestures of support.

When Secretary of State Cyrus Vance was here last month to seek progress on the protracted strategic arms limitations talks, the subject of the dissidents was not even raised in formal sessions.

Orlov, acting under the guarantees contains eerie echoes of past clashes of the 1975 Helsinki accords that the Krelmin signed, founded a group in 1976 to monitor Soviet compliance. Since then, the group has issued more than two dozen reports alleging such violations as religious repression, use of psychiatric hospitals as political prisons, arbitrary refusal to allow reunification of families by emigration, and substandard living conditions in criminal work camps.

The state has Iobeled the group's activities "anti-Soviet agitation and propaganda," a charge used often, through the 60 years of Communist Party rule, to silence political opponents.

Ginzburg and Schansky also were members of the Helsinki monitoring group, but each had other activities that angered the Soviets.

Ginzburg administered a fund to aid political prisoners and their families with royalties from the works of exiled nobel prize-winning novelist Alexander Solzhenitsy. Scharansky, a computer technician, is a Jew who was denied permission to emigrage to Israel on security grounds.

Scharansky has been charged with treason, a capital crime, and the Kremlin has accused him of being employed by the CIA. Carter personally denied this, but in the view of dissidents and other observers here, the Kremlin gained enormous ground with the recent admission by Washington that the CIA had in fact been in contact with a man named Sonay Lipavsky. Lipavsky said he was a dissident but later denounced Scharansky and several American journalists working here.

The trial of Orlov, 52, a physicist, between the Kremlin and its critics. The presiding judge, V.G. Lubentsova, handled the trial of some young Russians who in 1968 demonstrated here against the Soviet invasion of Czechoslovakia.

Sofia Kalistratova, 71, a lawyer who has represented dissidents in the past described Judge Lubentsova as a woman who "in external manner conducts herself correctly,"

But Kalistratova added: "I'm deeply convinced the sentence comes from the very top. No doubt, the sentence is already decided."

The trial is likely to last no more than three days, since a number of Orlov's friends have been sent out of the city for three days beginning Monday on what are euphemistically known as "working trips." Others who might be expected to try to get a seat in the court have been warned not to be absent from their jobs "for even one hour," according to Irina Ginzburg, wife of Alexander Ginzburg.

Orlov's lawyer, chosen for him by his relatives, according to Kalistratova, is Evgeny Shalman, whom she described as being in his late 40s, a lawyer of 25 years' experience and "qualified and of good conduct." This will be his first political case, she said.

Virtually nothing is know of the detailed accusations of the charge against Orlov. This is because of a law making it a crime for anyone to disclose such information before trial without court permission.

Kalistratova speculated that the case is based on reports of the Helsinki monitoring group alleging human rights abuses.

"According to Soviet law, it is not a crime to criticize the basis of the system or to express one's opinion. It becomes a crime only if the purpose is to weaken or subvert the state." she said.

It is also a crime "if the person confirms something to be true which isn't," she said. "If he says there is religious repression and the authorities hold this to be a lie, he is guilty."

Thus, for example, witnesses could be persons who assert to the presiding judge and two lay judges - there is no jury that there is no such repression. "The legal structure is built to create an impression of democracy and legality," said Kalistratova, "In Practice, "they don't observe this in the case of the state. For them, the truth is dangerous, because here we have a totalitarian state."

This view is shared by non-dissident Soviet sources as well. On such person, a party member, asserted, "They want to liquidate dissidents, and any organization of them . . . They want to show the strength of the government."