The first criminal trial of a coal company on charges of faking the dust samples that indicate the risk of dread black lung disease has ended in a devastating defeat for the federal government.

The Justice Department isn't expected to appeal, partly because an appeal, if granted would bring the prosecutors before the same trial judge whose rulings undermined their case. And acquittals on the two crucial conspiracy counts are unappealable.

Thus a final victory for Consolidated Coal Co., the nation's second-largest coal producer, may be at hand, four years after a grand jury in Columbus, Ohio, returned a 172-count indictment against Consol and eight employes.

Consol, a Continental Oil Co. unit based in Pittsburgh, declined to comment. By contrast, Arnold Miller, president of the United Mine Workers of America, issued a statement charging that the case, even if lost "because of insufficient evidence," helped to air "the real problem...the coal operators' disregard for the miner's life."

The case began when Paul (Tex) Bobak, a former Consol environmental technician, tipped federal mine-safety inspectors to evidence of alleged systematic cheating on dust samples taken in the company's five underground mines in a three-county area in the vicinity of Georgetown, Ohio.

After getting search warrants, agents seized the evidence in simultaneous "raids" in May 1974 and followed up with an investigation and the indictment.

Essentially, the investigators found a scheme that they say was operated this way by the individual co-defendants and three unindicted co-conspirators, Bobak and two other environmental technicians:

Dust samples were allegedly discarded or "voided" if weighing found them "heavy" with the microscopic particles that cause black lung. Substitute samples, which sworn testimony said were falsified in various ways to indicate that dust levels were within the limites allowed under the Federal Coal Mine Safety Act of 1969, then were sent off for monitoring by an unsuspecting Mining Enforcement and Safety Administration.

Prosecutors dropped charges against one defendant, Richard Schrickel pleaded guilty to two misdemeanor charges of falsifying the individual miners' data cards that accompany the samples; he awaits sentencing. Another environmental technician, Samuel L. Kirkland, pleaded guilty to a misdemeanor count and was fined $500. Afterward, Schrickel and Kirkland testified for the prosecution.

Bobak's former boss, environmental engineer Darrel. R. Hazelwood, and environmental technician James A. Kull went to trial, were convicted in 1977 on the two conspiracy counts, and were fined $1,000 and $750, respectively.

Not until last March 19 did a separate jury trial begin for the remaining defendants: Consol; Raymond J. Zitko, safety director of the Central Division and the highest-ranking employe indicted: chief environmental technician Francis Leo Marks, and environmental technician Robert W. Lasick.

The reason for the delay was that U.S. District Court Judge Robert M. Duncan had dismissed the four defendants on the ground that the search warrants used in the 1974 raids were unconstitutional. The 6th U.S. Fircuit Court of Appeals reversed him, but the defendants twice carried the issue-unsuccessfully-to the Supreme Court.

On March 20, the day selection of a 12-member jury was completed, Duncan dealt the first of a series of blows to Justice Department lawyers Richard I. Chaifetz and Lauren Kahn. Grating defense motions, he:

Ordered the prosecutors not to mention the words "black lung" because "its injection into the trial can only...arouse the jury's passion." Prevention of black lung was a primary purpose of the 1969 law. By estimate of the United Mine Workers, the three separate diseases clustered under the name-pneumoconiosis, bronchitis and emphysema-directly kill at least 4,000 coal miners a year.

Struck 142 counts of the indictment, each of which alleged a crime: violation of a mandatory health standard. Duncan held that each alleged violation was of a prescribed procedure for dust sampling, and that, he said, isn't crime.

In the trial, key testimony came from Lowry Blackburn, vice president of Consol's Central Division, and Richard Rouse, who became president of the division in January, 1974.

Blackburn testified that he had delegated to safety director Zitko, as to Zitko's predecessor, responsibility for compliance in the underground mines with the dust-sampling requirements of the 1969 law. Rouse testified that he didn't alter that arrangement.

But there was no testimony to indicate that the protection of the approximately 2,000 underground miners from blacklung was a high priority of company executives. Indeed, some miners testified that until the May 1974 raids precepitated a cleanup, dust levels were so high when continuious-mining machhines were used that they could hardley see even a few feet.

The government completed its case March 29. Outside the presence of the jury, Consol then moved for a directed verdict of acquittal on the ground that no one in a policymaking position in the company had been shown to have been aware of or to have condoned violations.

The government protested that Consol was making a see-no-evil, her-no-evil defense amounting to this: by keeping itself ignorant it had avoided criminal liability.

Judge Duncan wondered if the government could show the Consol had bebefitted from the violations. Prosecutor Chaifetz suggested that it had benefitted, in that compliance with the law takes time and effort away from prodction and therefore can reduce revenues.

Finally, however the judge acquited Consol. At the same time, he also acquitted Zitko.

With the chiefs out of the case, the only remaining defendants were two low-level employes, Marks and Lasick. On April 2, after deliberating about two hours, the jury acquitted them.