WASHINGTON — The transmission of now-classified information across Hillary Rodham Clinton's private e-mail is consistent with a State Department culture in which diplomats routinely sent secret material on unsecured e-mail during the past two administrations, according to documents reviewed by the Associated Press.
Clinton's use of a home server makes her case unique and has become an issue in her campaign for the Democratic presidential nomination. But it is not clear whether the security breach would have been any less had she used department e-mail. The department only systematically checks e-mail for sensitive or classified material in response to a public records request.
In e-mails about the 2012 attack on a US diplomatic facility in Benghazi, Libya, department officials discussed sensitive matters in real time, including the movement of Libyan militias and the locations of key Americans. The messages were released last year under the Freedom of Information Act and are posted on the State Department's website.
An e-mail from diplomat Alyce Abdalla, sent the night of the attack, appears to report that the CIA annex in Benghazi was under fire. The e-mail has been largely whited out, with the government citing the legal exemption for classified intelligence information. The existence of that facility is now known; it was a secret at the time.
In an e-mail sent at 8:51 p.m. on Sept. 11, 2012, Eric J. Pelofsky, a senior adviser to then-UN Ambassador Susan Rice, gives an update on efforts to locate US Ambassador Chris Stevens, who died in the attack.
The e-mail was marked unclassified when sent. Later, part of it was deemed classified and censored before its release.
In five e-mails that date to Condoleezza Rice's tenure as secretary of state during the George W. Bush administration, large chunks are censored on the grounds that they contain classified national security or foreign government information.
In a December 2006 e-mail, diplomat John J. Hillmeyer appears to have pasted the text of a confidential cable from Beijing about China's dealings with Iran and other sensitive matters. Large portions of the e-mail were marked classified and censored before release.
Clinton insists she did not send or receive classified information. But government officials have found material they deem classified in several dozen of 30,000 e-mails that the former secretary of state has turned over, an unfolding saga that has dogged her 2016 campaign.
Many of the e-mails to Clinton containing classified information were forwarded to her by a close aide, Huma Abedin. Most, however, originated with diplomats who have access to confidential material. Some e-mails sent by Clinton have since been censored.
Such slippage of classified information is ''very common, actually,'' said Leslie McAdoo, a lawyer who frequently represents government officials and contractors in disputes over security clearances and classified information.