Schmitt was born November 2, 1959, in Minneapolis, Minnesota, and raised in the Bay Area. His B.A., in political science and third world development, was awarded by Williams College in 1982.
He worked reporting on education at the Tri-City Herald of Kennewick, Washington, for a year.
In 1983 he became an employee of The New York Times, and has remained such since. For about his first year, his position was as the clerk of James Reston, the senior columnist. He covering a variety of areas from 1984 to 1990, including an investigation of HUD affairs in Puerto Rico the spring of 1990.
In 1990 he took the title of Pentagon Correspondent, including covering the Gulf War in early 1991, Somalia in December 1992, and Haiti in September 1994.
In 1996 he became a domestic correspondent covering the United States Congress and immigration.
Upon the September 11 attacks in 2001, he returned to covering the Pentagon, focusing on U.S. national security. As of 2010 his assignment is the war on terrorism.
Schmitt is notable for breaking the story that the Obama administration was planning to reverse the Bush policy of holding captives in extrajudicial detention in American internment facilities in Afghanistan, without allowing them to learn why they were being held. On September 12, 2009, Schmitt, quoting officials who did not want to go on the record by name, that Bagram captives would be allowed to request to review and challenge the allegations that lead to their detention.
In 2004 Schmitt reported that on the fears of rape held by female GIs in Iraq at the hands of their fellow GIs. Schmitt was interviewed by National Public Radio on the DoD's response to the GI's fears.
Schmitt was one of the New York Times journalists who played a key role in reporting the homicide of several Afghan captives in U.S. custody at the Bagram Air Base internment facility in 2003 and 2004.
In 2006 Schmitt and a colleague reported on bribery concerns that involved Major Gloria Davis, an officer in the United States Army who was found dead from a gunshot wound shortly thereafter.
A New York Times article he wrote on Task Force 373 was killed, according to Julian Assange but the topic was covered by Der Spiegel and The Guardian.