Who killed Joffrey?
It seems clear, from Littlefinger’s discussion with Sansa (III: 767-769), that he arranged for the poison to be secreted in the hairnet he had Dontos bring to her for a third party to pick up and drop into Joffrey’s drink at an opportune time. In general various Tyrells are blamed for the attempt. Lady Olenna was certainly the only one who had an opportunity to take the poison from the hairnet, as she adjusted it when meeting Sansa and Tyrion outside of the feasting hall (III: 672, 673). But it’s argued that Margaery, being right next to Joff and his cup, had a greater opportunity to place the poison in his cup with the added argument that, given that she was expected to share drinks with him from the chalice, it’d be safer if she herself put in the poison. Some suggest Ser Garlan, Margaery’s brother, may have been the true culprit. Although he was seated even further from the newlyweds than Lady Olenna was (III: 674), he was near the chalice when it was briefly left unattended for the
