What you're about to read may sicken you. It will certainly anger you.

This is a story of justice, or what passes for it in the contemporary United States. It's also a story of international relations and how diplomacy sometimes works against justice.

The story begins in the early morning hours of Jan. 21, 1994 in Houston. On that cold morning, a man flagged down a police officer and told him that he had just been robbed. The robbery had taken place in the parking lot of a dance club on the southwest side of the city. Officer Guy Gaddis of the Houston Police Department drove to the scene of the robbery. There he found two men who fit the description of the robbers.

The two men were taken into custody and, according to police, searched repeatedly before being handcuffed and put in the back of the patrol car. But somehow, the procedures failed that morning and one of the suspects managed to hide a pistol in his pants.

Details of how the suspect was handcuffed and where exactly he hid the pistol were not readily available as I was writing this. But this is not an officer safety case study; it's a story of crime and punishment.

The crime was heinous. As Officer Gaddis transported those two men to the Harris County Jail for booking, one of them shot that young officer three times, twice in the back of the head and once in the neck.

Gaddis had just completed two-and-a-half years of service on the Houston PD. He was a Desert Storm Army veteran. His wife was pregnant. And at 24, he was dead.

The man who pulled the trigger and ended Officer Gaddis' life was Edgar Tamayo, 26. Last month, 20 years and one day after the crime, he finally went to the death chamber.

You may be thinking 20 years is an awful long time from conviction to execution for a cop killer in Texas, which is very proactive when it comes to capital punishment. And you'd be right to think so.

The Tamayo death sentence has been one of the most convoluted executions in Texas history. Here's the rub. Tamayo was a Mexican national who was illegally in the United States. And UN treaty law involving consular notification was not properly followed after his arrest.

So in addition to being a cause for the usual anti-death penalty attorneys, Tamayo had Mexican government officials in his corner. They claimed that even though the Mexican Consulate in Houston was notified 10 days before trial that the notification was too late to satisfy the requirement of the UN treaty and also too late to have any effect on the outcome of the trial. Specifically, the Mexican government believes that a more prompt notification of the consulate would have given Mexican officials more time to find witnesses that might have testified on Tamayo's behalf during the penalty phase of the trial.

One thing is clear: Those witnesses would not have been testifying that Tamayo was a gentle and loving soul. Prior to murdering Gaddis, he served time in California for robbery and parole violations. Instead, what Tamayo's supporters argue is that he was too mentally retarded to execute.

Tamayo may have had a low IQ, but when it came to killing he was a savant. Somehow he managed to hide that handgun on his person and prevent its discovery during officer pat-downs. Then he managed to pull that gun while cuffed, aim it at Gaddis' head, and without hesitation fire twice at point-blank range. So he was pretty adept when it came to perpetrating lethal violence.

Because of the international treaty issues, the Tamayo case was heard in the Hague where The International Court of Justice ruled that it violated treaty law. Both President George W. Bush and Secretary of State John Kerry argued that Texas should grant an appeal for a new hearing out of fear that other countries would use the case as an excuse to violate the treaty rights of Americans arrested abroad. And the night of the cop killer's execution the case landed in the U.S. Supreme Court, which decided not to grant a stay.

So Tamayo was given a lethal injection. And afterward, Officer Gaddis' brother gave a statement to the press in English and Spanish offering condolences to the Tamayo family. Which was a really classy thing to do. Mexican officials on the other hand expressed support for the cop killer's family and railed against the execution.

You may now vomit or punch a wall or write a strongly worded letter.