• Police can ask a judge for search or arrest warrants.police line image by cico from Fotolia.com
  
  A warrant is a writ issued by a judge or magistrate directing someone to act. Under the Fourth Amendment to the Constitution, people are guaranteed the right to be free from unreasonable searches and seizures. Along with the Constitution, state and federal laws govern how warrants can be used by the state.
  
  

Arrest Warrants

• In general, only a judge or magistrate can issue an arrest warrant. The Fourth Amendment provides that "no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."
  
  Because of these requirements, all arrest warrants issued must be accompanied by an oath, typically in the form of an affidavit or complaint. States typically codify these requirements in specific laws about criminal procedures. For example, South Dakota Code § 23A-2-1 requires all warrants to include a written statement of facts that constitute the criminal offense charged, and be signed under oath.
  
  

Search Warrants

• Like arrest warrants, search warrants must also comply with state and federal warrant laws requiring specificity, support by an oath and probable cause. Unlike arrest warrants, search warrants can be directed at a place or property instead of a person. Typically, states require law enforcement officers serving such search warrants to "knock and announce" their presence before entering a structure. However, there are exceptions. For example, South Dakota Code § 23A-35-9 allows magistrates to issue "no-knock" warrants if there is probable cause to believe announcing the presence of law enforcement before the search would result in harm to persons or property.
  
  

Unreasonable

• So what happens if someone is arrested or searched without a warrant? In cases such as Mapp v. Ohio, courts have ruled that unreasonable searches and seizures are unconstitutional and any evidence gained from such state actions is inadmissible in court.
  
  However, while unreasonable searches and seizures are unconstitutional, what makes state activity unreasonable varies. For example, courts have held that law enforcement officers who do not have a warrant but who observe criminal activity or notice contraband material in plain sight do not violate a person's right to be free from unreasonable searches and seizures. Further, consenting to the state's search request is also not considered a violation of a person's Fourth Amendment rights (see, for example, Georgia v. Randolph).