Convictions Overturned for 5 Leading South African Black Activists : Apartheid: They are freed from prison and are greeted by singing colleagues.

Five leading anti-apartheid activists, convicted last year in a historic treason trial that dealt a sharp blow to black protest in South Africa, were freed from prison Friday after the country’s highest court overturned their convictions.

“We’re overjoyed to be back with our families,” Popo Molefe, 37, general secretary of the United Democratic Front, said in an interview on the plane taking him home to Johannesburg. “But it’s unfortunate we had to lose four years of our lives to prison when it was so patently clear from the beginning that we had committed no crime.”

The men, including two other senior UDF leaders, were greeted in Johannesburg by more than 400 black, white, Indian and mixed-race activists who clogged the airport arrival hall, singing liberation songs and holding up freshly painted signs saying, “Welcome Home Comrades.”

As the freed men were carried away on the shoulders of the crowd, policemen scuffled with well-wishers, briefly arresting several people, including the Rev. Allan Boesak, who had gone to the aid of a woman bitten by a police dog.

The 1988 convictions, after one of South Africa’s longest and most important political trials, were overturned by the Appeal Court in Bloemfontein. The court ruled that the trial judge, Kees van Dijkhorst, had improperly dismissed one of two legal experts assisting him as being too sympathetic to the UDF. The assistant had signed a UDF petition in 1983 opposing a new constitution that excluded blacks from representation in Parliament.

In Cape Town, lawyers, family members and friends greeted the men as they arrived on a ferry from Robben Island prison. At the Cape Town airport, Anglican Archbishop Desmond M. Tutu led the men and their supporters in a prayer.

“We thank you, Lord, that the halls of justice have vindicated our brothers,” the 1984 Nobel laureate said.

Judge Van Dijkhorst, who presided over the 3 1/2-year trial, ruled that the UDF plotted to violently overthrow the white minority-led government. He said UDF protests had led directly and intentionally to bloody township riots that swept the country in the years 1984-86.

The case acquired prominence as a trial of the 2-million-member UDF itself and, by implication, other government opponents who considered themselves part of the liberation struggle. The front, formed in 1983, is a multiracial coalition of more than 600 anti-apartheid groups.

Twenty-two defendants, including clergymen, teachers and community leaders from the Vaal River region south of Johannesburg, where the first wave of unrest flared five years ago, were charged with treason, subversion, terrorism and murder. Half were acquitted at various stages.

The Appeal Court action overturned the remaining 11 convictions, including those of six men who had received suspended sentences for terrorism. The three UDF leaders and one of their co-defendants, a church worker, had been sentenced to terms ranging from six to 12 years for treason. A fifth man, a member of a UDF-affiliated group, was convicted of terrorism.

Most of the defendants were granted bail during the trial, but the judge denied bail for the three UDF leaders, who have been in prison since their arrests in 1985.

Human rights lawyers, calling the appeal ruling “an excellent victory,” demanded that the government disclose how much was spent on “this abortive prosecution, which took years of blundering incompetence to achieve nothing but red faces.”

The UDF, which the government said was the internal wing of the outlawed African National Congress, has been effectively banned since February, 1987, under state-of-emergency regulations. But in recent months President Frederik W. de Klerk has loosened the grip on anti-apartheid activity, allowing dozens of rallies, including those organized by recently freed leaders of the ANC.

“If the regime thought it was breaking the movement by bringing these charges in the first place, it made a serious mistake,” Molefe said. He said the freed men intend to return to active roles in the anti-apartheid struggle.

Those freed Friday, in addition to Molefe, were Patrick Lekota, 41, the front’s publicity secretary, Moses Chikane, 41, secretary of the Transvaal branch of the UDF, the Rev. Tom Manthata, 49, a church field worker, and Gcinu Muzi Malindi, of the UDF-affiliated Vaal Civic Assn.

They were imprisoned on Robben Island in Cape Town harbor, where many political prisoners have been held. Lekota and Chikane have daughters who were born after they were imprisoned in 1985 and have never seen their fathers as free men.