Edgar Arias Tamayo took 17 minutes to die.
The 46-year-old Mexican national was taken into the Texas execution chamber, strapped down and given a lethal injection which would eventually kill him.
He didn't have any final words to say, instead choosing to remain silent.
Tamayo, who was convicted of the 1994 shooting and killing police officer Guy Gaddis, 24, as he was being arrested for robbery was in the US illegally.
His execution went ahead despite objections from the US and Mexican governments arguing it violated international law, ignoring a 2004 court order from the International Court of Justice.
The ICJ argued that Edgar Tamayo, along with other Mexican nationals, was not informed of his right to seek consular advice without delay following his arrest.
This move denied him assistance that anti-death penalty advocates say could have provided crucial evidence in the case.
In 2008 a psychologist put Edgar Tamayo's intellectual functioning in the "mild mental retardation" range, which would render his execution unconstitutional under US law.
He was put to death regardless while his victim's mother and four other relatives looked on, the BBC reported.
Tamayo is just one of dozens of prisoners and people who have been put to their deaths across the globe so far this year.
In the past 2 weeks alone, inmates have been killed in countries such as Iran, Iraq, and the USA, which are among the top 5 states in the world carrying out the death penalty, according to Amnesty International.
Just this week Iraq was under the human rights spotlight after reports emerged of 12 secret executions carried out by authorities, bringing the number of prisoners put to death since Sunday 19th January to 38.
Amnesty claim many of those executed were convicted after grossly unfair trials, in which 'confessions' were extracted under torture and then used as evidence in court.
Most of those executed were convicted on charges of terrorism under the 2005 Anti-Terrorism Law.
Neighbour Iran carried out a total of 40 executions since the beginning of 2014, with at least 33 carried out in the past week alone.
Amnesty said it represented an alarming spike considering Iran was trying hard to change its image in the international community.
In the week since 9 January this year, more officially acknowledged executions were carried out here than during the whole month of January 2013.
At least 1 of these executions have been carried out in public this year, which normally sees the inmate lifted by a noose around the neck in front of a crowd and hanged.
Closer to home, Vietnam is set to add to those numbers after it sentenced 30 men and women to death on Tuesday for drug smuggling in the biggest drugs trial to take place in the country.
Vietnam executed its 1st prisoner to death last August following a 2-year hiatus in carrying out capital punishment due to difficulties obtaining chemicals for lethal injections.
The convicted drug smugglers join more than 700 others now estimated to be on death row in the south-eastern Asian nation.
Amnesty International spokeswoman Sarah Saleh said the number of executions which had taken place so far this year was certainly alarming.
"Amnesty opposes the death penalty in all cases, without exception," Ms Saleh said.
"It is a violation of every human being's right to life and is a cruel, inhuman and degrading punishment."
She added authorities must urgently take steps to abolish the death penalty, which has been shown again and again not to have any special deterrent effect on crime.
"Rather than continuing to hand down death sentences, these countries should be moving towards abolition, in line with the global trend," she said.
Source: news.com, January 27, 2014