A Chilean Army lieutenant today was ordered to remain in jail on a manslaughter charge pending probable trial by a military court in the death of Rodrigo Rojas, the 19-year-old District resident who was fatally burned, allegedly by troops, during antigovernment protests on July 2.

Lt. Pedro Fernandez Dittus was also accused by investigating Judge Alberto Echavarria of negligence leading to grievious bodily harm to student Carmen Quintana, 18, Rojas' companion who is in critical condition at a hospital here.

Lawyers for the victims' families saying they would appeal the ruling as insufficient, accused Echavarria of "grave offenses to the law and the principle of judicial impartiality." According to lawyers Hector Salazar and Luis Toro, from the human rights office of the Roman Catholic Church, Echavarria based his findings only on the testimony of the soldiers involved in the incident, ignoring evidence provided by more than 12 eyewitnesses.

Two other officers and five noncommissioned officers were released without charge. Echavarria then handed it over to military court, which must make its own formal charges before trial. Members of the military accused of offenses carried out while on duty can only be tried in military court.

On Monday, Echavarria released 17 conscripts whom the Army had detained with the officers last Friday.

Echavarria corroborated the official Army version of the incident, that Rojas and Quintana were detained by a military patrol in the early hours of the two-day protest strike, and that they were burned accidentally when a Molotov cocktail they were carrying exploded.

Civilian witnesses said the two were beaten, drenched with gasoline by their assailants and set afire, after being caught with a group of youngsters who were preparing to build a barricade of tires.

Rojas was working as a photographer while on his first visit to his homeland after 10 years' exile with his family in Washington.

The two were found severely burned on another side of the city. Echavarria said the fact that they were not given immediate treatment but were left in "a place and in conditions unpropitious for obtaining such attention" gave reason to believe Fernandez, as commander of the patrol, had been guilty of negligence.

Previous cases passed to the military courts have failed to result in convictions.