In the United States, police are permitted to search you, without a warrant, following a lawful arrest.
Massachusetts statutory limits the scope of such searches.
Under G.L. c. 276, Sec. 1,
A search conducted incident to arrest may be made only for the purposes of seizing fruits, instrumentalities, contraband, and other evidence of the crime for which the arrest has been made, in order to prevent its destruction or concealment; and removing any weapons that the arrestee might use to resist arrest or effect his escape. Property seized as a result of a search in violation of the provisions of this paragraph shall not be admissible in evidence in criminal proceedings.
According to the Supreme Judicial Court, the statute,
authorizes a search to be made incident to an arrest only (1) for the purpose of seizing evidence of the crime for which the arrest has been made in order to prevent its destruction or concealment or (2) for the purpose of removing any weapon the person arrested might use to resist arrest or to escape. Commonwealth v. Blevines, 438 Mass. 604, 607 (2003), quoting Commonwealth v. Wilson, 389 Mass. 115, 118 (1983).
Police cannot use a search incident to arrest for “investigatory purpose unrelated to the crime for which the defendant [is] being 16 arrested.” Blevines, supra at 609.