There is an interesting article in the newest Historical Research, which adds to scholarship on  mid-fourteenth century law and legislation on treason: D. Crook, ‘The seditious murder of Thomas of Sibthorpe and the Great Statute of Treasons 1351-2.’ Historical Research 88 (2015) deals with the killing of a prominent royal servant, who had occupied the positions of Chancery clerk,  clerk of Parliament, justice of assize and justice of the peace. Sibthorpe was found to have been crushed or smothered in bed, by a group including a man who was supposed to be rendering an account to him. Because of his status as a sworn royal officer, this was treated as sedition, with consequent upping of the penalties of some of the homicides from hanging to hanging plus the extras associated with the traitor.  Crook makes a convincing case for the likely influence of this case (and that of Sir John de Eland) on those drawing up the Statute of Treasons, thus supplementing the account in J. G. Bellamy, The Law of Treason in England in the Later Middle Ages (Cambridge, 1970).