By Elliott Gotkine
BBC South America correspondent
Argentina's Supreme Court has ruled there is no time limit when it comes to prosecuting crimes against humanity.
Enrique Arancibia Clavel was convicted of murder
The landmark decision upholds the life sentence given to one of the murderers of Gen Carlos Prats, an ex-Chilean army chief killed in Buenos Aires in 1974.
The ruling is also seen as upholding a Congress decision to annul some of the amnesty laws protecting former members of the country's military dictatorship.
Estimates say some 13,000 people died in the 1976-83 "dirty war".
Overturning Argentina's controversial amnesty laws has been one of President Nestor Kirchner's top priorities ever since he assumed power in May last year.
Persuading the country's upper house of Congress to back him on this proved reasonably straightforward but for the decision to become law, it needs the support of the Supreme Court.
Argentina's highest tribunal is expected to rule in the coming months, but the finding in the Prats case is widely being seen as the biggest hint yet that the court will uphold Congress' decision.
Lawyers for Enrique Arancibia Clavel, the Chilean secret police agent accused of planning the murder of Carlos Prats, had argued that their client should never have faced trial.
They said too much time had elapsed between the crime being committed and the case coming to court.
But five of the eight Supreme Court judges disagreed, ruling that the case could be tried retroactively because there is no statute of limitations for human rights crimes.
Legal experts believe the ruling could now pave the way for the successful prosecution of some of the military dictatorship's key players, many of whom are accused of kidnapping, torture and murder.