MEXICO CITY -- A former state police officer and his son were freed from Mexico's maximum-security prison early yesterday after a judge dismissed charges that they helped assassinate the governing party's former presidential candidate, Luis Donaldo Colosio.
The exoneration of Vicente Mayoral Valenzuela and his elder son, Rodolfo Mayoral Esquer, left the authorities holding only one of five suspects they originally charged with conspiring to kill Colosio as he left a campaign rally in the northern city of Tijuana on March 23, 1994.
Government officials said they expected prosecutors to appeal the ruling, but it was unclear how much damage the judge's decision might have done to the government's case.
The four suspects who have been exonerated were all members of a crowd-control team formed by the local branch of Colosio's governing Institutional Revolutionary Party.
They were arrested on the basis of testimony from Colosio's bodyguards and videotapes of the rally that officials interpreted as showing the men helping to trap the candidate for his confessed killer, a young Tijuana factory worker.
Since the arrest of a second purported gunman this year, officials familiar with the investigation say that it has focused on a more elaborate conspiracy, one involving higher-profile suspects. But they have offered almost no new evidence.