Thus, the incitement may be implied as well as express and may be directed to persons generally. The test is whether there is a lawful use for the device. For example, a recording or transcribing device may be used lawfully without breaching copyright, but a device to detect radar signals so as to avoid speed camera/red light infringement systems would have no other purpose than assisting drivers to evade detection. But note that the act incited must be a crime by the person incited so any alleged breach of copyright would have to be criminal, and the defendant would have to know all the material facts that would make the incited person's behaviour criminal, but not that the behaviour was a crime (see the public policy "ignorantia juris non-excusat" which prevents ignorance of the law from being an excuse). In "R v Whitehouse" an uncle did not incite his 15-year-old niece to incest because, if the incitement had succeeded and she had submitted to intercourse, she would not have committed an offence. This applied "R v Tyrell" which stated that where a statutory offence is designed to protect a particular class of individuals against themselves, they cannot, as the victims, commit such offences against themselves. In "Tyrell", the girl was not guilty of inciting the man to have under-age sex with her, since the girl could not herself be guilty of the full offence.