The boards of appeal have developed in their case law certain principles as to the standard of proof required to establish the facts on which a decision is to be based. In some decisions the boards of appeal have applied the standard of "the balance of probabilities", which means that in relation to, for example, the question of when a document was first made available to the public, the board must decide what is more likely than not to have happened (see T 381/87, OJ 1990, 213; T 296/93, OJ 1995, 627; and T 729/91 of 21 November 1994). In other decisions the boards have taken the view that a fact has to be proved "beyond reasonable doubt" or "up to the hilt" (see T 472/92, OJ 1998, 161; T 97/94, OJ 1998, 467; T 750/94, OJ 1998, 32). More recent decisions dealing with the implications in practice of applying these two different standards of proof are T 2451/13 (for "up to the hilt") and T 545/08 (for "balance of probabilities"). See also T 842/14 (novelty and standard of proof).