If you mean complicit...
An individual is complicit in a crime if he is aware of its occurrence, has the ability to report the crime, but fails to do so. As such the individual effectively allows criminals to carry out a crime despite easily being able to stop them, either directly or by contacting the authorities, thus making him a de-facto accessory to the crime rather than an innocent bystander.
Law relating to complicity varies. Usually complicity is not a crime although this sometimes conflicts with popular perception. At a certain point a person that is complicit in a crime may become a conspirator depending on the degree of involvement by the individual and whether a crime was completed or not.