Development: On 17 September Mexican authorities reported that Gildardo ‘El Gil’ López Astudillo, considered a key participant in last year’s abduction and presumed murder of 43 training teachers in Iguala, Guerrero state, had been arrested. Significance: The arrest and earlier news that the remains of one of the missing students (the second so far) had been identified through DNA testing carried out by the University of Innsbruck in Austria have raised hopes of progress in resolving one of Mexico’s most notorious and politically sensitive crimes. But the Iguala case remains as complex and disputed as ever. As the first anniversary…