The 27-page report, which was obtained by The New York Times, found that Mr. Hynes potentially violated the City Charter and conflict of interest board rules; violations of the City Charter can be charged as misdemeanors. Mr. Hynes’s conduct may have also violated the state penal code section on official misconduct. And payments from the office to the consultant, Mortimer Matz, may have violated the larceny provisions in the penal code. Under the code, any larceny of more than $1,000 is a felony.

In 2012 and 2013, Mr. Matz’s firm was paid $219,824 for “public relations and communications services rendered.” Investigators said that during that period, Mr. Matz “provided few if any actual public relations and communications services to the office,” adding that the consultant served “primarily if not exclusively as a political consultant to Hynes personally.”

The investigation found that in 2013, the office typically issued two or three checks each month to Mr. Matz’s firm from state asset-forfeiture funds; from 2003 through 2013, investigators said, the district attorney’s office paid the firm about $1.1 million from those funds. State law requires that asset-forfeiture funds be used only for law enforcement purposes.

The inquiry, which began in November, included the review of about 6,000 emails sent to or from Mr. Hynes’s official email address for the 18-month period before the 2013 general election.

Mr. Hynes’s emails paint a picture of a man who, after two dozen years in office, used staff members, colleagues and whatever resources he could tap to help shape what was an ultimately unsuccessful campaign against Kenneth P. Thompson.