(Miriam Carey during a trip to Niagara Falls in 2007, when a butterfly las landed on her shoulder. (Courtesy of Valarie Carey))

A conservative watchdog group filed a federal lawsuit Tuesday seeking to force the U.S. Justice Department to turn over investigative documents in the case of Miriam Carey, the unarmed motorist who was shot to death on Capital Hill by Secret Service agents and Capitol Police officers in October 2013 following a chase from the White House.

Judicial Watch’s complaint in U.S. District Court for the District of Columbia alleges that the Justice Department has failed to respond properly to a request made under the Freedom of Information Act in August 2014 by WorldNetDaily.com, or WND, the conservative online news outlet that is Judicial Watch’s client.

Last July, following an investigation assisted by the Metropolitan Police Department, the U.S. Attorney’s office announced its finding that the officers did not use excessive force in violation of Carey’s rights.

Carey, 34, a dental hygienist from Stamford, Conn., whose infant daughter was in a car-seat at the time, drove past a Secret Service kiosk into a restricted area off 15th Street NW. Officers ordered her to stop and tried to block her with a portable fence, but she turned down Pennsylvania Avenue NW toward the Capitol. Near the West Lawn, she struck a Secret Service vehicle with her car, and officers fired a volley that missed. Outside the Hart building, she was hemmed in and shot five times as she drove in reverse towards officers.

(The of Miriam Carey’s car as she attempts to leave a White House security kiosk on 15th Street NW, Oct. 3, 2013, while an off-duty Secret Service officer attempts to stop her with a portable fence. (U.S. Attorney’s office))

Some family members said Carey suffered post-partum depression a year before her death. Around that time, she told Stamford police that President Obama had her condo under surveillance. However, her family and colleagues at two dental practices said she acted normally and responsibly up to the day she died.

None of the agencies involved have ever publicly explained the officers’ use of deadly force. Surveillance videos outside the White House and the Capitol that captured portions of the seven-minute drama have been withheld.

According to the Judicial Watch complaint, the Justice Department notified WND in March that its request for documents “is waiting to be assigned and processed” along with “other requests that are before yours.” The complaint alleges that, under the law, WND was owed a determination on its request last September, which would have permitted WND to have appealed any denial by now.

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“It’s time for the Justice Department to live up to its name and bring justice, openness and closure to the Miriam Carey tragedy,” WND chief executive officer Joseph Farah said in a statement.

A spokesman for Justice Department declined to comment.

(Valarie Carey, sister of Miriam Carey, joins family members and friends in a protest on the first anniversary of Miriam’s death this past October. (Linda Davidson/The Washington Post))

The Post also has a pending Freedom of Information request with the Justice Department seeking information about the incident.

Eric Sanders, a civil rights attorney representing Carey’s family, previously filed a $150 million wrongful-death civil claim. Sanders said Wednesday that in the coming months he will convert the claim into a lawsuit against the Secret Service, the Capitol Police and possibly other agencies.