WHEN PRESIDENT BARACK Obama nominated Sonia Sotomayor to replace the retiring Justice David Souter on the U.S. Supreme Court in May 2009, he listed Sotomayor's work as a New York City prosecutor as one of her biggest qualifications for the job. "Sonia learned what crime can do to a family and a community," Obama declared, "and what it takes to fight it."
For libertarians, it was an ominous statement. Would Sotomayor turn out to be yet another Supreme Court justice with an unduly deferential attitude toward law enforcement? It looked like a distinct possibility. As New York University law professor Kenji Yoshino told the Los Angeles Times in June 2009, "I think her experience as a prosecutor balances out her liberal tendencies."
But Sotomayor defied that expectation. In fact, over the past seven years, she has distinguished herself as one of the Supreme Court's most outspoken critics of police misconduct and one of its most consistent champions of the Fourth Amendment.
Take the 2015 case of Mullenix v.
Luna, in which the Court granted qualified immunity to a police officer who used deadly force to end a high-speed car chase. In a lone dissent, Sotomayor lambasted her colleagues for "sanctioning a 'shoot first, think later' approach to policing [that] renders the protections of the Fourth Amendment hollow."
That same year, during oral arguments in Rodriguez v. United States, Sotomayor practically read the riot act to a Justice Department lawyer who insisted that police officers...