For evidence to be admissible in a criminal prosecution it generally must have been obtained legally—with a search warrant, or based on an exception to the search warrant requirement, such as consent to search—and be relevant and reliable.
In New Hampshire, as in other states, the admissibility of evidence in a criminal prosecution is governed by both state statutes and federal law, including the Fourth Amendment to the U.S. Constitution. Evidence must generally be obtained legally for it to be admissible in court. This means that law enforcement officers are typically required to obtain a search warrant before conducting a search to collect evidence. However, there are several exceptions to this requirement, such as when an individual gives consent to a search, when evidence is in plain view, during exigent circumstances, or when the search is incident to a lawful arrest. Additionally, the evidence must be relevant to the case, meaning it must have a tendency to make a fact more or less probable than it would be without the evidence, and it must be reliable, ensuring that it is trustworthy and has a clear connection to the crime. New Hampshire courts will exclude evidence that is obtained in violation of these principles, often referred to as the 'exclusionary rule', to prevent the use of illegally obtained evidence and to uphold the integrity of the judicial process.