The Justice Department has been dealt two legal setbacks stemming from its controversial prosecution of black civil-rights activists in Alabama, who charged that they were targeted for racial reasons.

In one case, the 11th U.S. Circuit Court of Appeals in Atlanta overturned the conviction of the only one of eight defendants found by a jury to have engaged in voting fraud.

The court said last month that Spiver Gordon had presented sufficient evidence that he and other black activists were targets of "selective prosecution" by the Justice Department. The court also held that prosecutors appeared to have acted improperly in repeatedly striking blacks from the jury that convicted Gordon.

In a second ruling last Tuesday, the appeals court reinstated a lawsuit by black plaintiffs seeking to challenge the Alabama prosecutions as racially and politically motivated.

"The department claimed they were trying to protect the voting rights of blacks, but they consistently struck blacks from the juries," said Ira A. Burnim, who assisted the defendants while he was an attorney for the Southern Poverty Law Center.

Justice Department spokesman Terry H. Eastland, who has consistently defended the investigations, said this week that he would have no comment.

The 1985 prosecutions of civil-rights activists in Alabama's rural "Black Belt" counties sparked charges that the Reagan administration was attempting to intimidate black voters in areas where they had attained political power.

The cases involved alleged tampering with absentee ballots, a voting device that had enabled blacks to win control of local offices in five of the 10 impoverished counties.

The defendants argued that federal authorities repeatedly ignored complaints that local white politicians had abused absentee ballots for decades.

A Senate committee last year rejected the judicial nomination of Jefferson B. Sessions III, U.S. attorney in Mobile, in part because of his prosecution of one of the voting-fraud cases. In that case, a jury acquitted Albert Turner, a former aide to the Rev. Martin Luther King Jr., along with Turner's wife and a third defendant.

In the other cases, prosecuted by U.S. Attorney Frank Donaldson in Birmingham, two defendants were acquitted, two pleaded guilty to misdemeanor charges and were placed on probation. Gordon, a City Council member in Greene County and national member of the Southern Christian Leadership Conference, was convicted on four of 21 counts of mail fraud and false information.

The appeals court panel voted, 2 to 1, to send Gordon's case back to the U.S. District Court. The Justice Department has not said whether it will retry him.

The court cited a Justice Department spokesman's statement "that the investigations were part of a 'new policy . . . brought on by the arrogance on the part of blacks' in these counties."

In addition, the court said, "Gordon presented evidence to show that the government targeted only those counties where blacks were a majority, specifically targeting those counties where blacks since 1980 had come to control some part of the county government."

The court said that "the members of the rival white political organization assisted law enforcement officials in their investigations of the Greene County Civil League, the principal political organization representing blacks, of which Gordon was a leader." It said Gordon had "sufficiently established" that he may have been the victim of "selective prosecution."

The court said it was also overturning the conviction because prosecutors used all six of their "peremptory strikes" to remove blacks from the jury. "The striking of a single black juror for a racial reason violates the Equal Protection Clause {of the 14th Amendment}," the court said.

"Those peremptory strikes followed a recurrent pattern of exclusions of black {jurors} in the government's other voting-fraud cases against black leaders . . . . In two similar voting-fraud prosecutions, the government had used five of six peremptory challenges to strike black jurors in one case and four of six to strike black jurors in the other," the opinion said.

In the suit, the plaintiffs accused the department of selectively prosecuting black leaders and of using "intimidating and harassing" tactics against black absentee voters, many of them elderly.

The department opposed the suit on "separation of powers" grounds, arguing that the courts should not intervene in executive branch prosecutions.

The appeals court disagreed, saying, "If the facts are as plaintiffs allege, this case presents one of those 'rare situations' in which federal court intervention in the prosecutorial and investigative process is appropriate."

It said the alleged injuries were as basic as "the chilling of the plaintiffs' right to vote."