Sheriff's office at Fairfax County Circuit Court. (Rich Lipski/The Washington Post)

NATASHA McKENNA, a 37-year-old woman who had been diagnosed as a child with schizophrenia, died Sunday, five days after she struggled with guards at the Fairfax County Adult Detention Center. The struggle ended when they shot her with a stun gun, apparently multiple times. As Ms. McKenna lay on life support in a hospital before dying, her mother took photos of her battered body — two black eyes, a missing or amputated finger, severe bruises running the length of her left arm.

Fairfax County authorities — the sheriff’s department, which runs the jail, and the police department are investigating — now face a choice: They can promptly release full details of the circumstances that led to her death, including video of the incident at the jail. Or they can delay, stonewall and attempt to evade accountability — a pattern of conduct in another recent case that has tainted the county’s reputation.

Ms. McKenna, an African American woman with a 7-year-old daughter, had a history of erratic behavior but no serious criminal convictions. She was detained Jan. 15 after making a commotion in public, then struggling with Alexandria police officers who tried to restrain her. She punched one officer in the face and tried to bite others.

Rather than jail her, Alexandria police did the sensible thing: They brought her to a local hospital for psychiatric evaluation, then moved her two days later to Inova Mount Vernon Hospital in Fairfax, where she received psychiatric care for several more days.

Then the system broke down. Rather than being transferred to a state psychiatric facility, Ms. McKenna was picked up on Jan. 26 by Fairfax County police. Acting on a felony-assault warrant from Alexandria for punching the cop, they delivered her to the detention center, the main jail in Fairfax. There she sat for eight days. Why?

The violent encounter took place Feb. 3, when the Sheriff’s Emergency Response Team — at least five officers in black helmets, visors and heavy padding — tried to transfer her to Alexandria.

According to Pete Earley, a writer in Fairfax who covers mental health issues, the officers entered her isolation cell, struggled with Ms. McKenna, who stood about 5 feet 3 inches tall and weighed 130 pounds, and shot her with the stun gun. Transported to a local hospital, she never regained consciousness.

Fairfax Sheriff Stacey Kincaid, who oversees the jail, Police Chief Edwin C. Roessler Jr. and Sharon Bulova (D), chairman of the county Board of Supervisors, are all promising a prompt and transparent investigation.

That must include releasing the video of the violent encounter (whose existence county officials confirm), the medical examiner’s report and relevant documents from both the sheriff’s and police department’s investigations. The public also deserves to know whether guards at the jail, including the emergency response team, have received training in crisis intervention — training that Ms. Kincaid, in­cred­ibly, has suggested is not important for officers who deal with inmates.

Full disclosure would be a departure from the county’s 18-month exercise in foot-dragging and obfuscation in the death of John Geer, the unarmed man shot by a Fairfax police officer in 2013 as he stood in the doorway of his home. The handling of Ms. McKenna’s death will determine whether the county has learned any lessons.