MORRIS THOMPSON
 Herald World Staff

 MEXICO CITY -- A lot of people expressed grief when Fernando Gutiérrez Barrios
 died recently of a heart attack at age 73, but not necessarily because they
 admired him.

 Gutiérrez, a federal senator from the ruling Institutional Revolutionary Party when
 he died, was the head of Mexico's secret police when government troops killed
 several hundred unarmed student protesters in a Mexico City plaza on the eve of
 the 1968 Summer Olympics here.

 REAL STORY

 The real story of the Tlatelolco Massacre, named after the site of the incident,
 may be the biggest mystery in Mexico's recent past, but it is only one of many
 crucial events that have never been cleared up. As the years pass, Mexicans fear
 that others who know the secret history of Mexico will take their secrets to the
 grave.

 Gutiérrez Barrios continued to run Mexico's secret-police agency, the now
 disbanded Federal Security Directorate, for many years afterward, and many
 Mexicans say he directed a little-known ``Dirty War'' in the 1970s, in which
 perhaps 1,500 leftists and suspected leftists were killed and another 600 or so
 disappeared.

 Rosário Ibarra, founder of a group of families of the disappeared, said she was
 sorry that Gutiérrez died just as Vicente Fox has become this country's first
 president from outside the PRI since 1928, because she hopes Fox will press to
 uncover the hidden history of Mexico's political life. Fox was elected after
 promising to bring honesty and accountability to Mexico's government. Many
 Mexicans expect that to include finding the answers to nagging questions about
 controversial events during the PRI's long reign, when the rich and powerful were
 seen as accountable to no one. That may not be easy, especially if records prove
 to be sparse, and bureaucrats and former officials are reluctant to tell what they
 know.

 One of the common elements in all the unsolved mysteries is that many
 Mexicans remain unconvinced by official accounts of what happened. Among
 them:

   When PRI presidential nominee Luis Donaldo Colósio was killed at a campaign
 stop in Tijuana in 1994, the official investigation concluded the gunman acted
 alone. The suspicion that the anti-reform wing of the PRI conspired to have
 Colósio killed remains popular, however.

   After Roman Catholic Cardinal Juan Jesús Posadas Ocampo was gunned down
 at the Guadalajara airport in 1993, officials said drug dealers had mistaken his car
 for that of one of their rivals. Posadas' successor said he thought there was a plot
 against the prelate, who was outspoken about the need for more democracy and
 less corruption, including in the war against drugs.

 FEDERAL BUDGET

   As a bank bailout in the mid-1990s mounted to $100 billion in a country whose
 annual federal budget is about half that, the government said it had acted merely
 to save the financial system from collapse. Then came revelations that individual
 PRI supporters had gotten loans they never repaid. A full accounting of who
 received loans and why has never been made.

 As for the Tlatelolco Massacre, the questions abound: How many were really
 killed? Who ordered the indiscriminate shooting? Why? Luis Echeverría, Gutiérrez
 Barrios' direct supervisor as minister of the interior, went on to become president
 in 1970, and many believe that he was the key figure in the event. But his role has
 never been cleared up and he has always denied responsibility.

 Fox has promised Mexicans they will get an accounting for the mysteries of the
 past, but has also said that Mexico's Congress will have to decide exactly how to
 provide one. Political analysts say PRI loyalists who don't want the past
 excavated and remain a power in the legislature could fight back by giving Fox
 trouble with other parts of his legislative and governing agenda.

 Fox named Mariclaire Acosta Urquidi, who's on leave as president of the
 respected nongovernmental National Commission for the Defense and Promotion
 of Human Rights, his special ambassador for human rights and democracy.

 "This new government has an obligation to help find these answers from the
 past,'' she said in an interview. ``I don't think there has been a real transition to
 real democracy anywhere in the world that hasn't come to terms with its past.''

 She said proposals under consideration include something like the Truth and
 Reconciliation Commission used by South Africa after apartheid ended. As in
 South Africa, the panel could require people to testify, with the condition that they
 would not be prosecuted for what they admitted. Such an effort is under way in
 Chile.

 "These matters are disparate on the surface, but they're part of the same process
 of impunity [that is, not holding the powerful or rich responsible for their actions]
 that had been happening to other people for a long time,'' Acosta said. "What
 was different in `93 and `94 [the Posadas and Colosio assassinations] was that
 the victims [were] prominent members of the church hierarchy and of the political
 system.''

 Acosta said she thinks a similar lack of accountability helps explain complicity
 with corruption.

 ``It's a systemic phenomenon,'' she said. ``This was a whole system that was
 created on the basis of impunity.''