In a fairly recent United States Supreme Court case, the Court had to resolve the issue of whether the police use of heat-seeking devices to detect whether the owner of a home was growing marijuana inside his residence constituted a search for Constitutional purposes.
The Constitution protects against unreasonable searches and seizures. The police used heat-seeking devices based on a tip that the owner of the home was growing marijuana inside his residence. The purpose of the heat-seeking device was to detect if the residence contained high-powered lamps usually used in residential marijuana growing cases.
The Court held that the heat-seeking device does constitute a search for Constitutional purposes and, therefore, the police are required to have something beyond mere suspicion to conduct the search.
The reason this case is important to the practice of criminal law is because this case stands for the proposition that when police use items that are generally not available to the public and those items or devices are used in an attempt to detect an individual engaged in criminal activity, the Court will find that a search has occurred.