As Brazil hurtles towards an official Covid-19 death toll of 5,00,000—second-highest in the world—science is on trial inside the country and the truth is up for grabs.

With the milestone likely to be reached this weekend, Brazil’s Senate is publicly investigating how the toll got so high, focusing on why President Jair Bolsonaro’s far-right government ignored opportunities to buy vaccines for months while it relentlessly pushed hydroxychloroquine, the malaria drug that rigorous studies have shown to be ineffective in treating Covid-19.