The execution of Edgar Tamayo Arias, scheduled to die Wednesday, puts at stake "Texas' respect for the Constitution of the United States and for international law," members of the International Commission against the Death Penalty wrote in an opinion piece published Sunday in the Latin Times.
Texas could violate the U.S. Constitution by executing Tamayo, convicted in 1994 of killing a Houston police officer, the article said, because he has been diagnosed with "mild mental retardation."
The authors of the article contend Texas violated the Vienna Convention on Consular Relations by failing to notify Mexican diplomatic officials of Tamayo's detention in 1994. Mexican authorities did not learn of his arrest until a week before his trial.
The article said there also were questions about the quality of Tamayo's defense, including a lack of testimony about abuse and physical injury he received growing up.
The case has attracted attention from the Obama administration and the International Court of Justice, the article said. U.S. Secretary of State John Kerry warned Tamayo's execution would be "extremely detrimental" to U.S. interests in a letter he wrote to Texas Gov. Rick Perry in September. Mexican officials have reportedly intervened, asking for a stay of execution and for Texas to abide by a 2004 ruling of the International Court of Justice the United States must review the convictions of 51 people sentenced to death.
The commission asked Texas to stay Tamayo's execution and review his case. It also asked the state to institute a moratorium on executions.
Members of the commission, which is supported by 18 nations, include Bill Richardson, the former governor of New Mexico, and Federico Mayor, former director of UNESCO and Spain's former director of education and science.