Judicial functions of the House of Lords

For centuries the House of Lords functioned as the United Kingdom's highest court, sitting as a court of first instance for the trials of peers and for impeachments and as a court of last resort for the United Kingdom and, before it, the Kingdom of Great Britain and the Kingdom of England. Its judicial role narrowed over time: originally any member could hear an appeal, but by the nineteenth century only trained legal professionals, the Law Lords, actually did so, a practice formalized by the Appellate Jurisdiction Act 1876, which created dedicated Lords of Appeal in Ordinary. The last trial of a peer took place in 1935, the procedure for such trials was abolished in 1948, and impeachment fell into disuse, before the Constitutional Reform Act 2005 transferred all of the House's appellate jurisdiction to the newly created Supreme Court of the United Kingdom on 1 October 2009, with the sitting Law Lords becoming its first Justices and no new Law Lords appointed thereafter.