It is well established by court decision that police in executing a search warrant may seize items not listed in the warrant if they observe such items in plain sight - and if it is immediately apparent to them that such items are evidence of crime. The Supreme Court has stated that there is a third requirement needed to justify police seizure of such items, namely that the discovery of the items must have been inadvertent, that is, accidental or unintentional. Therefore, if the police were seeking items not set out in the warrant, their discovery could not be inadvertent. The issue is whether the warrantless seizure of evidence of crime in plain view is prohibited by the Fourth Amendment if the discovery of the evidence was not inadvertent. The Supreme Court concluded that even though inadvertence is a characteristic of most legitimate "plain view" seizures, it is not a necessary condition.