However, even these specific statutory exceptions have proven unavailing to knife owners at times. It is important to note that "good reason or lawful authority" exceptions may be difficult to establish for those not using a knife in the course of their trade or profession, but merely because the knife is needed in case of emergency or for occasional utility use. Although English law insists that it is the responsibility of the prosecution to provide evidence proving a crime has been committed, an individual must provide evidence to prove that they had a "good reason or lawful authority" for carrying a knife (if this is the case) upon being detained. While this may appear to be a reversal of the usual burden of proof, technically the prosecution has already proven the case (prima facie) by establishing that a knife was being carried in a public place (see Violent Crime Reduction Act 2006 on Knives, etc.; New powers to tackle gun and knife crime)  As the burden of proving "good reason or lawful authority" lies with the defendant, it is likely that an individual detained and searched by the police will need to prove the following (sometimes known as the "THIS" list): Has "THIS" person got permission; to use "THIS" article (knife); for "THIS" use; on "THIS" land; and by "THIS" land owner. The special exception which exists in the Criminal Justice Act 1988 (Sec. 139) for folding knives (pocket knives with non-locking blades) with a cutting edge (not blade) less than long, is another "common sense" measure accepting that some small knives are carried for general utility; This exemption however only applies to folding knives without a locking mechanism. The wording of the Criminal Justice Act does not mention locking and so the definition of "folding pocket knife" was settled through case law. In the Crown Court appeal of "Harris v. DPP" (1992) and the Court of Appeal case of "R. v Deegan" (1998) the ruling that 'folding' was intended to mean 'non-locking' was upheld. As the only higher court in England and Wales to the Court of Appeal is the Supreme Court, the only way the decision in "R. v. Deegan" could be overturned is by a dissenting ruling by the Supreme Court or by Act of Parliament. The Offensive Weapons Act 1996 covers the possession of knives within school premises:  The Offensive Weapons Act 1996 imposes an age restriction on the sale of knives:  The Criminal Justice Act 1988 (Offensive Weapons) (Exemption) Order 1996 states restrictions to sales of knives to those under 16 does not apply to: These age restrictions in the Criminal Justice Act 1988 were increased to 18, effective from 1 October 2007, by the Violent Crime Reduction Act 2006.