Natasha McKenna (Courtesy of Natasha McKenna's family)

EVEN BEFORE the violence a year ago in Ferguson, Mo., after the police killing of Michael Brown, many law enforcement agencies across the country responded to incidents involving the use of deadly force by proactively releasing dashcam, body-camera and other video footage when it existed. The idea, as a top police official told The Post after video of a 12-year-old boy killed by a rookie patrol officer in Cleveland was released days after the incident in November, is “in the spirit of being open and fair with our community.”

By a quick, partial and unscientific scan of Google, we see videos released by police and other law agencies involving fatal incidents over the past 18 months in Boston; Tulsa; Gardena, Calif.; Longview, Tex.; North Charleston, S.C.; Albuquerque ; and, in the recent arrest of Sandra Bland — who later died in jail in an alleged suicide — Prairie View, Tex.

If only the authorities in Fairfax County had gotten the message.

In Fairfax, nearly six months after the fact, officials in the police, sheriff’s and prosecutor’s offices continue to withhold from the public a video depicting an in-custody struggle at the county jail between guards and Natasha McKenna, a mentally ill inmate. Ms. McKenna, who was shot repeatedly with a Taser stun gun after she had been handcuffed, never regained consciousness; she died five days later, on Feb. 8.

Sheriff Stacey A. Kincaid, whose office runs the jail, and Police Chief Edwin C. Roessler Jr., whose department conducted the investigation, both pledged their commitment to candor and transparency. So why haven’t they released the video, which sources tell us runs more than 30 minutes and captures much of the prolonged confrontation that led to Ms. McKenna’s death?

Mr. Roessler, for his part, has said the video cannot be released because it is “evidence.” But the videos in Boston, Tulsa, Gardena, Longview, North Charleston, Albuquerque and Prairie View were also “evidence.” The authorities in those places released them nonetheless — and in most instances, they did so quickly.

In a number of those incidents, police and other law enforcement officials appear to conduct themselves professionally. Other incidents are embarrassing for the police, portraying what looks like indefensible and possibly criminal use of force, including in the killing of Walter Scott, an unarmed man shot in the back in North Charleston as he tried to flee from an officer after a traffic stop in April.

In addition to releasing videos, in most cases authorities also publicly identified the officers involved. In many, the officers involved were placed on administrative duty or leave until the outcome of the investigation.

In Fairfax, none of the six sheriff’s deputies who struggled with Ms. McKenna have yet been identified, either by name or by race. (Ms. McKenna was black.) In Fairfax, not one was placed on administrative duty or leave. In Fairfax, mum’s the word.

Here’s the relevant question for Fairfax authorities: Are they content to brand the county and its law enforcement agencies as among the least accountable in the nation?