The photos of two weary looking men dressed in prison uniforms appeared in the newspaper here the other day under a headline labeling them "dangerous counterrevolutionaries."

"As if they were tired of taking up arms against the people, two mercenaries from the FDN listen to charges brought by the prosecution," said a caption, using Spanish-language initials for the Nicaraguan Democratic Force, the main U.S.-backed group fighting against the Sandinista government.

The two, identified as Victor Altamirano and Santos Borge, were the latest defendants to go before Popular Anti-Somocista Tribunals, the Sandinista government's widely criticized emergency courts for those accused of security-related crimes and rebel activities.

The Managua-based tribunals, a three-judge panel and a three-judge appeals panel, fall outside Nicaragua's ordinary court system. Their decisions, reached under abbreviated procedures, cannot be reviewed by the Supreme Court. Each tribunal is made up of one lawyer, who presides, and two untrained Sandinista militants picked by the government from neighborhood militias or neighborhood Sandinista Defense Committees.

As a result, the Inter-American Commission on Human Rights has charged that it has "serious doubts" whether the tribunals guarantee due process. The Nicaraguan Permanent Human Rights Commission, an independent group often hostile to the government, has described the system as an instrument of political coercion reminiscent of abuses by the dictatorship of the late Anastasio Somoza.

"They are tribunals of political vengeance," said Lino Hernandez, a lawyer who is the commission's national coordinator. The justice system "was political during Somoza's time, and it is political now."

Sandinista officials explain the tribunals as part of a war-imposed emergency in which traditional Nicaraguan standards of evidence and defendants' rights cannot be maintained. Other countries also have curtailed judicial guarantees during war or other crises, they point out.

"It was for the emergency" that the tribunals were created, said Armengol Cuadra, 31, president of the appeals panel. "If the emergency disappeared, the tribunals also would disappear."

Sandinista supporters also point out that, despite questionable practices and political criteria in their judgments, the tribunals should be judged in the context of Central America's frequently faulty judicial systems. Moreover, they point out, even bad tribunals are better than the death squads that are part of antisubversion efforts in neighboring El Salvador or Guatemala.

About 850 Nicaraguans, including top rebel leaders, have been charged before the tribunals since they went into operation to expedite trials in June 1983. Of those, 25 have been found innocent during their trial and 14 more on appeal, according to tribunal records. Eighty-six others have been amnestied or pardoned after conviction, the records show.

Most of the rest are serving prison terms from three to 30 years or remain in jail awaiting trial, Cuadra said. Thirty years is the maximum sentence, and there is no death penalty under the penal code revised by the Sandinistas.

Other defendants are being tried in absentia. Among these are former colonel Enrique Bermudez, the FDN's Honduras-based military leader; Adolfo Calero, its top political figure, and Eden Pastora, who was a Sandinista hero as "Commander Zero" before becoming disenchanted and starting another rebel army opposed to the Nicaraguan government based in Costa Rica.

Hernandez said a major complaint is that most defendants come to trial after several months in prison, where they are interrogated by the Interior Ministry's General Directorate of State Security, and that the primary evidence against them is a confession obtained during the interrogations.

The Lawyers Committee for International Human Rights, an independent U.S. monitoring group, cited a case in which it said the tribunal accepted the confession of a Nicaraguan optometrist, taken after he had been held incommunicado for two months, even though the defendant later denied to the court that it was valid.

The optometrist, Alejandro Pereira, was convicted of spying for the rebels and sentenced to 15 years. After Amnesty International protested, Hernandez said, Pereira was pardoned last fall and has since moved to Costa Rica.

Most defendants have been Nicaraguans arrested for supporting or participating in the insurgency, Cuadra said.

"They are all counterrevolutionaries," he added.

Altamirano and Borge, whose trial was reported in the progovernment Nuevo Diario newspaper, were accused of fighting with the FDN in northern Nicaragua. The newspaper's report on their appearance before the tribunal reflected the political atmosphere that has contributed to criticism of the panels.

"Both defendants participated in the criminal and unlawful activities of the FDN in the provinces of Jinotega and Matagalpa," it said, without mentioning whether they had admitted the charges or denied them.