Colombia's Supreme Court began hearing arguments Monday in the trial of a retired army general accused of taking part in the 1989 assassination of a top presidential contender.

Miguel Maza was head of Colombia's intelligence agency when Luis Carlos Galan was assassinated while campaigning in a poor suburb of Bogota. Maza is accused of taking payments from Pablo Escobar's Medellin drug cartel to reduce the candidate's security detail ahead of the fateful campaign stop at which he was riddled with bullets.

Galan, a cartel-fighting politician whose youthful good looks and idealism drew comparisons with John F. Kennedy, was heavily favored to win Colombia's highest office at the time of his slaying.

Maza, who has been jailed since 2013, denies any wrongdoing and said that he himself was a target of several cartel assassination plots.

The trial comes as Colombians re-examine the role of corrupt state agents in several high-profile killings during the apex of drug-fueled violence two decades ago.

That includes last year's exhumation of former guerrilla Carlos Pizarro, who was slain 25 years ago while running for president. Family members and political allies have long accused bodyguards assigned by the state of standing by as an assailant opened fire on Pizarro in a crowded airliner midflight.

Authorities also last month dug up remains of three people killed in the army's siege of the Palace of Justice in 1985 after guerrillas raided the building and took members of the Supreme Court as hostages. Witnesses say several of the suspected assailants and witnesses were seen being escorted from the building alive and are believed to have been later killed by army officers.

"These aren't isolated incidents," Sen. Juan Manuel Galan, the politician's son, told The Associated Press. "There's a common thread linking all these crimes."