When does the simple digital tracking of your location and movements start to be truly revealing? When do the data points and inferences that can be drawn from it strongly suggest, say, trips to a psychiatrist, a mosque, an abortion clinic, a strip club or an AIDS treatment center? The answer, according to a new research paper, is about a week, when the data portrait of a person becomes sufficiently detailed to (37) as an “unreasonable search” and a potential violation of an individual’s Fourth Amendment rights. The research paper, a collaboration of computer scientists and lawyers, wades into the debate over the legal and policing implications of modern data collection and analysis technology. It explores (38) in legal circles is called the “mosaic theory” of the Fourth Amendment, which essentially states that when linked and analyzed by software, a much richer picture emerges from combined information than from discrete data points. The main technology for making these inferences is machine learning, a branch of artificial intelligence. In the paper, the authors write that their goal was “to identify the (39) at which enough is enough—the point at which long-term government surveillance becomes objectively unreasonable.” The issue of when location data and analysis might (40) a violation of the Fourth Amendment came up most prominently in a Supreme Court case, United States v. Jones, in 2012. In the case, Antoine Jones, a nightclub owner in Washington, D.C., was suspected by the police of dealing drugs. The local police, working with federal agents, put a GPS tracking device on his car, without a warrant, and gathered his location data for four weeks. Mr. Jones was (41) convicted of drug trafficking conspiracy, based in part on thousands of pages of location information sent from the GPS tracker over 28 days. But then the Supreme Court ruled for Mr. Jones, saying his Fourth Amendment rights had been violated because placing the GPS device on his car, without a warrant and without his knowledge, was “an unauthorized physical intrusion,” as if someone had come into his home.