Texas executes Mexican national

The argument was not new. Texas, the nation's most active death-penalty state, has executed other condemned foreign nationals who raised similar challenges, most recently in 2008.

Leal's appeals focused on legislation introduced last month in the U.S. Senate by Vermont Democrat Patrick J. Leahy. Leahy's measure would bring the United States into compliance with the Vienna Convention on Consular Relations provision regarding the arrests of foreign nationals and ensure court reviews for condemned foreigners to determine if the lack of consular help made a significant difference in the outcome of their cases.

President Obama's administration took the unusual step of intervening in a state murder case when Solicitor General Donald Verrilli Jr. last week joined Leal's appeal in asking the high court to halt the execution and give Congress at least six months to consider Leahy's bill.

"The legislation would give Mr. Leal an opportunity to demonstrate that with consular assistance, he likely would not have been convicted, let alone sentenced to death," Sandra Babcock, a Northwestern University law professor and one of Leal's lawyers, said.

Leal's attorneys had the support of the Mexican government and other diplomats who believed the execution should be delayed so his case could be thoroughly reviewed. Some also warned that Leal's execution would violate the treaty provision and endanger Americans abroad.