The murder of a Mexican teenager has sparked a fierce legal debate about how to protect human rights on the Mexico-US border. In 2010, US Customs and Border Protection (CBP) agent Jesús Mesa gunned down a 15-year-old Mexican national, Adrián Hernández Guereca, as he approached the US border in El Paso, Texas, from Ciudad de Juárez, in Mexico’s Chihuahua state. For years, various US courts have been debating whether Mesa can be prosecuted for killing Hernández under US law. This month, the case is due to go to the US Supreme Court for a final ruling. Hernández’s parents have asked…