In any case, he said, the cellphone video does not represent new evidence, since it was known to investigators and was disclosed to the family in response to the wrongful-death lawsuit they filed in the case. The suit was settled in 2016 for $1.9 million.

A number of questions were also raised after Ms. Bland’s death about what happened at the jail, and why a 28-year-old woman on her way to start a new job would take her own life.

Most of those questions have already been put to rest: Both her mental health background and the physical evidence in the autopsy report pointed to suicide.

The confrontation at the traffic stop led to Ms. Bland being arrested on a charge of assaulting a public servant. She was booked on July 10, 2015, into the Waller County jail in Hempstead, a town of about 6,000 in southeast Texas, and she was placed in a housing area for women.

Three days later, on July 13, a guard making the rounds found her hanging in her 15-by-20 foot cell in what officials described as a “semi-standing position,” with a plastic trash-can liner around her neck and affixed to a U-shaped metal hook overhead. She was pronounced dead shortly after 9 a.m.

The results of the autopsy, announced by officials on July 23, indicated that her injuries were consistent with suicide, not homicide. The autopsy found that the condition of Ms. Bland’s head, neck and hands lacked any signs of a violent struggle. Markings around her neck were also consistent with suicide, the medical examiners said.

Waller County officials later expressed regret that Ms. Bland had not been placed on suicide watch, particularly in light of her disclosure on a jail screening form that she had once tried to kill herself with pills after losing a baby. She also reported at the time she entered the jail that she had battled depression and was feeling depressed at the time.