Colosio Assassination Plot Alleged : Mexico: Aburto’s father claims his son is being made the fall guy in a broad conspiracy.

Less than two weeks before the assassination of Luis Donaldo Colosio, a former state police officer who later served on the Mexican presidential candidate’s security squad invited the man now accused of slaying Colosio to attend a meeting, according to the father of the alleged assassin.

Ruben Aburto said in an interview that his son, Mario Aburto Martinez, the confessed killer of Colosio, was asked to the session by Vicente Mayoral Valenzuela, one of a group of former policemen recruited to provide crowd control during the candidate’s fatal campaign swing in Tijuana on March 23.

“He (Mayoral) invited him to a meeting of a committee,” the elder Aburto told reporters from The Times and two Mexican newspapers late Saturday in San Pedro, the Los Angeles harbor community where the father lives. “He told him that delegates from all over the (Mexican) republic would be there.”

While his son didn’t specify to his father what the meeting was to be about, the use of the words “committee” and “delegate” strongly suggest a political theme in Mexico.

Aburto’s family maintains that he is being made the fall guy for a broader assassination plot, perhaps after having been recruited by others. Mexican officials have dismissed such a conspiracy, and relatives have no proof.

Mexican authorities seeking potential accomplices in the attack are believed to be focusing on the approximately 45-member volunteer security squad at the Tijuana campaign stop.

Mayoral, a 30-year veteran of the Baja California state judicial police, was arrested in the melee immediately after the killing but was later released after federal authorities said he was merely a witness who helped subdue the gunman. He has not been officially charged in the case.

Relatives of Mayoral’s say federal authorities whisked the former police official and his son, Rodolfo Mayoral--who also served on the Colosio security detail in Tijuana--to Mexico City last week for questioning. The family vehemently denies any wrongdoing by either man.

Another security detail member, Tranquilino Sanchez Venegas, has been arrested and charged as a “co-participant” in the slaying, although his alleged role has never been clarified. In photographs taken moments before the assassination, Sanchez is seen near Colosio and Aburto.

The security contingent was assembled by the Tijuana branch of Mexico’s Institutional Revolutionary Party, known as PRI, which has governed Mexico since its creation in 1929. As the PRI’s nominee, Colosio was a heavy favorite to win the presidential election scheduled for Aug. 21.

PRI officials in Tijuana have denounced the killing and offered full cooperation in the investigation.

The elder Aburto, 47, said he discussed the matter of Mayoral with his son in the family’s Tijuana residence March 11 or 12, when the father was visiting. Ruben Aburto said he advised his son not to attend any meeting, and he said he wasn’t sure if Mario went to the session. He also said he counseled his son to sever his relationship with Mayoral.

Authorities have generally depicted Aburto as a lone gunman, possibly deranged, who may have shot Colosio in a twisted effort to publicize his pacifist views.

Jose Luis Perez Canchola, human rights ombudsman for Baja California, has accused officials of using details of Aburto’s life as a “smoke screen” to conceal details of the extremely sensitive case.

Times staff writer Sebastian Rotella contributed to this story.