The court on Monday refused to hear an appeal from Rosa Estela Olvera Jimenez.
She was sentenced in 2005 for the death of a nearly 2-year-old boy she had been babysitting in Austin, Texas. The boy died three months after choking on five paper towels lodged in his throat. Jimenez said the boy ate the paper towels, but prosecutors argued that she stuffed the towels into the boy's mouth.
Mexico's new president, Enrique Pena Nieto, filed a brief in his personal capacity asking justices to reevaluate her case. But the court, without comment, refused to hear her appeal.