In this file photo, then-U.S. Secretary of State Hillary Clinton testifies before the Senate Foreign Relations Committee about the department's FY2013 international affairs budget February 28, 2012. (Chip Somodevilla/GETTY IMAGES)

HILLARY RODHAM CLINTON has served as first lady, a senator from New York and secretary of state. She is no newcomer to the corridors of power. Her decision to exclusively use a private e-mail account while secretary suggests she made a deliberate decision to shield her messages from scrutiny. It was a mistake that reflects poor judgment about a public trust.

Under the rules as they existed during Ms. Clinton’s time as secretary, from 2009 to 2013, government officials were not strictly required to use official e-mail accounts. However, in 2011 the White House spokesman, Jay Carney, said, “We are definitely instructed that we need to conduct all of our work on our government accounts . . . .” He said it was “administration policy” to use government accounts. Did this not apply to Ms. Clinton at the State Department?

If government officials did use private e-mails for public business, they were required to consider the e-mails to be equivalent to government records and to preserve them. Ms. Clinton took her e-mail with her when she left office in 2013, and then, in December, when asked by the State Department, turned over 55,000 pages of e-mails from the private account. Her spokesman said that in cases when she wrote to department officials at their formal addresses, those e-mails should still be in the department’s system. President Obama signed amendments to a law last November that require government employees who use private e-mail for official business to forward it to government systems within 20 days.

Ms. Clinton is not the first high-ranking government official to write private e-mails about public business. But a host of questions arise from her decision to use private e-mail exclusively while serving as secretary. How secure was the private e-mail? What was her motive? Did anyone ask why the secretary of state was breaking with an announced administration policy? Why did she not turn over the e-mails promptly upon leaving office? Has she withheld anything?

It may be that Ms. Clinton used private e-mail because she anticipated Republicans would be on the prowl for scandal and wanted to control what part of her record might be scrutinized. Such fears would have had ample basis, but they do not excuse a penchant for control and secrecy that she has exhibited before — and that remains a worrying attribute as Ms. Clinton possibly enters a presidential campaign. Nor is fear of partisan criticism an even remotely valid excuse for using a private channel for official business.

There in lies the real problem. Ms. Clinton essentially privatized her e-mail, reserving to herself the decision of what should be in the record. M s. Clinton’s spokesman said she followed the “ letter and spirit of the rules .” The letter, perhaps, was followed, but certainly not the spirit. If people aspire to public service, they should behave as stewards of a public trust, and that includes the records — all of them. Ms. Clinton’s use of private e-mail shows poor regard for that public trust.