When Helen Mack arrived at the scene of the crime, she found her older sister, Myrna, lying dead, just a few blocks from where she worked here. She had been stabbed 27 times.
Helen knelt down, placed her forehead on her sister's, and vowed to bring to justice whoever had done this. Twelve years later, Ms. Mack says she is close to completing that goal.
Nine years after an Army sergeant was convicted of the crime, three high-ranking military officers are on trial for allegedly ordering him to do it. The case, which opened last Tuesday, is being heralded as pathbreaking for Guatemala's justice system.
"This is the first time that someone is being tried in Guatemala for using their authority and position in a state entity to order a murder," says Guatemalan human rights lawyer Fernando Lopez.
Guatemala's 36-year civil war between the government and leftist guerillas ended in 1996, but many here say the military still wields considerable power, a power that critics say amounts to impunity.
"This case is already a success because military officers have been put on trial," says Mr. Lopez. "This strengthens the justice system because it shows that members of the military can also be held accountable to justice."
Myrna Mack was an anthropologist who had been conducting research on groups of indigenous people displaced by the war's violence. The prosecution charges that she was killed because the work she was doing was affecting the miltary's ability to carry out its operations against the rebels.
Prosecutors are trying to prove that, because of the military chain of command, retired Gen. Edgar Godoy, and retired Cols. Juan Valencia and Juan Oliva ordered Sgt. Noel de Beteta to kill Ms. Mack in 1990. The accused maintain their innocence and deny knowing Mack or her work.
Getting the case to court, Helen Mack says, was a long and painful task that has cost some $3 million. The defense filed a long series of objections during the pretrial process, postponing the court date for years.
Helen Mack left the country for two months before the trial after she says a high-ranking member of government warned her of a plot to kill her. Her lawyer says that unknown assailants shot at his home weeks before the trial began.
In the process of pushing her sister's case, Helen Mack has converted herself from a self-described apolitical, conservative business executive into a prominent justice advocate.
"The life I led before my sister's assassination didn't allow me to perceive the reality that the majority of Guatemalans face," Mack says, referring to citizens' typical encounters with the justice system.
In 1992, Helen Mack's work won her the Right Livelihood Award, often called the alternative Nobel Peace Prize. With the award money she founded the Myrna Mack Foundation, which works towards strengthening the Guatemalan justice system and has helped fund this case.
Some here fear that the international attention surrounding the case could impede the defendants chance of getting a fair trial. "I believe in the justice system and think this case will strengthen it, but I am worried that all the international pressure there has been will sway the judges decision," says defendant Juan Oliva.
Human rights activists say they hope the trial can serve to make public information about the military's wartime activities, in addition to establishing the guilt or innocence of three of its former officials.
The three accused and the man already convicted belonged to the presidential guard, which has been accused of carrying out covert counterinsurgency operations. General Godoy was its director at the time of Mack's death. The accused say that the entity's sole responsibility was handling the president's security.
Human rights activist Frank LaRue says establishing the role of the presidential guard in a courtroom is a crucial point. "Public opinion already accepts that this organization carried out clandestine operations and intelligence...," he says. "For a court to accept them will have an enormous impact."
Mack says that regardless of the trial's outcome, she is content knowing she has done her best.
"Last month I dreamt of my sister," she says. "She was worried about my safety. But then she hugged me and smiled, and I imagined that she was satisfied."