Why did the House of Commons use an ordinance of attainder against William Laud?

The House of Commons utilized an ordinance of attainder against William Laud because they were unable to secure a conviction through standard legal proof.1

During the English Civil Wars, the trial of the Archbishop—which was managed by his long-time adversary William Prynne—faced significant procedural difficulties. Faced with these challenges, the Commons resorted to an ordinance of attainder, a legislative act that allowed for a conviction without the necessity of a formal trial or traditional evidence. This measure was accepted with hesitation by the House of Lords, ultimately leading to Laud’s execution on January 10, 1645.21