A ruling by a Salvadorean court could affect Reagan administration efforts to win congressional support for doubling military aid to the Central American nation.
The case of five former Salvadorean National Guardsmen accused of murdering four US churchwomen was sent by an appellate court back to a lower court for more evidence.
The appellate judge apparently acted in accordance with at least one interpretation of Salvadorean law. But this may be lost on many North Americans - including leading members of Congress, who may regard it as one more example of Salvadorean foot dragging in the highly publicized case.
It is perhaps too early to assess the full implications of the court's decision on US politics, but already there are expressions of shock on Capitol Hill, where President Reagan's call for $110 million in military aid to El Salvador is already in jeopardy.
Many legislators are skeptical about the wisdom of spending more money to support the government in El Salvador at a time when it is under sharp attack for human-rights violations. The court decision can only enhance that skepticism.
After all, the case is more than two years old. The four women, three Roman Catholic nuns and a lay Catholic worker, were murdered in December 1980. Early investigations, including that of the US Federal Bureau of Investigation, implicated the five National Guardsmen.
Over the months, as the case dragged through the Salvadorean court system, there have been repeated charges that the courts were not acting fast enough, not using the evidence available, and not willing to prosecute the five guardsmen.
Ironically, the technicality on which the case was bounced back to a lower court centers on that court's failure to provide ''important evidence that is vital to the case.'' Judge Luis Alonso Melara of the appellate court said there was enough evidence to proceed with a trial on murder charges.
He added, however, that ''we also have to consider the charge of rape. In addition, there was apparently robbery of the nuns' effects. There is also the question of property damage, since their car was burned.''
Under Salvadorean law, the judge pointed out, ''All these charges must be brought in a single trial. A substantial amount of new evidence is needed before we can go forward.''
Judge Melara suggested that the speed with which the new evidence can be processed depends on the lower court and the public prosecutor. He refused to speculate on how long these steps may take.
But Salvadorean cases tend to drag on - and it is unlikely that witnesses can be located and reinterviewed quickly.