Secret Service Director Julia Pierson testifies before the House Oversight Committee as it examines details surrounding a security breach at the White House. (J. Scott Applewhite/AP)

SECRET SERVICE Director Julia Pierson promised a congressional committee that her agency would conduct a vigorous and comprehensive review of security lapses at the White House. “It will never happen again,” she pledged. But her halting performance at Tuesday’s special hearing was far from reassuring given recent revelations of embarrassing, and potentially disastrous, incidents involving this critical agency.

Internal reviews are no longer sufficient; it is time for independent analysis of what went wrong and what that says about the protection afforded to the president, his family and their historic residence.

For more than three grueling hours, Ms. Pierson was questioned by the House Committee on Oversight and Government Reform. “I wish to God you protected the White House like you’re protecting your reputation today,” said Rep. Stephen Lynch (D-Mass.), offering what seemed a bipartisan assessment. True, Ms. Pierson was constrained in publicly discussing sensitive security matters, and there is always an element of showmanship to such hearings. Particularly uncalled-for were bloodthirsty suggestions that agents shoot on sight anyone who breaches the White House perimeter, no matter the perceived threat.

But lawmakers were not wrong in decrying the lack of candor, even the duplicity, in Secret Service accounts of the Sept. 19 incursion by a fence-jumper into the White House and an earlier 2011 incident in which the service failed to properly investigate shots fired at the White House. Why, for instance, did the Secret Service report that the intruder was unarmed when he had a knife? Why imply he was apprehended just inside the entrance when he actually had raced through several rooms?

Nor were lawmakers wrong to wonder whether there are systemic problems at the agency. Consider the Virginia couple who crashed a state dinner in 2009; the agents who allegedly visited prostitutes in Cartagena, Colombia, while preparing for a presidential visit in 2012; the agent sent home from a Netherlands assignment in March after reportedly passing out drunk in a hotel hallway. The first intrusion into 1600 Pennyslvania Ave. in modern times — by a man who had previously been arrested with multiple guns and a map to the White House. And now, reports that a man with a gun and criminal record was allowed by a clueless Secret Service onto an elevator with President Obama.

Ms. Pierson was appointed to reshape the agency after the Colombia scandal. But as Rep. Elijah Cummings (D-Md.) told her, the culture clearly isn’t fixed when people in her agency feel comfortable telling Congress, not Secret Service leadership, about problems in the agency. Committee Chairman Darrell Issa (R-Calif.) was correct in calling for an independent review. Mr. Obama or Homeland Security Secretary Jeh Johnson should get one started forthwith.