"They have not heard from Mexico," Lomartire told Murdock on Monday.

Feeling as if she had exhausted all avenues, Lomartire asked the judge to admit Hernandez's testimony from past trials. But Murdock refused because some of the juror questions that caused Perez and Canela's convictions to be overturned were based on her testimony.

If she couldn't be in the courtroom to answer such questions, those unanswered questions could affect jurors in a third trial.

"The only way you can get her is if you get her from Mexico," Murdock said.

Mark Cheshire, spokesman for the Baltimore state's attorney's office, declined to comment about the ongoing case. The Department of Justice didn't return a request for comment. A spokesman for the Mexican Embassy also declined to comment.

Michael Griffith, an international criminal defense attorney based in New York, said it's difficult to get a suspect — let alone a witness — extradited from Mexico unless a U.S. attorney is pushing the case. He said embassies of the two countries are overburdened with similar requests.

"It's tough enough to get witnesses to come to court, let alone one in Mexico," said Griffith, best known for representing Billy Hayes, whose experiences in Turkish jail became the subject of the movie "Midnight Express."

If Canela and Perez face a third trial, they will be tried separately for the first time. Perez is slated to go first on March 11, while Canela's trial could start April 3.