HEMPSTEAD, Tex. — A 28-year-old woman whose arrest this month during a traffic stop ended with her hanging death in a county jail cell told officials that she tried last year to kill herself, the Texas sheriff who oversees the jail said on Wednesday. But the jailers did not put her on suicide watch, and her family’s lawyer said that relatives had no evidence that she had ever tried to commit suicide or struggled with depression.

The back-and-forth over the mental state of the woman, Sandra Bland, came a day after Texas authorities released a dashboard camera video showing how a stop for changing lanes without signaling escalated into a shouting match and struggle between Ms. Bland, who was African-American, and a white state trooper, Brian T. Encinia.

Some legal experts who reviewed the video raised questions about whether Ms. Bland, who was moving to Hempstead from the Chicago area to take a job at a local college, should have ever been arrested.

“This whole thing could have been avoided,” said Christopher C. Cooper, a civil rights lawyer, former Washington police officer and a recognized expert in police conflict resolution. He said that the video showed that the trooper’s decision to stop Ms. Bland for a minor infraction was legal but questionable, and that the officer’s angry, forceful response to Ms. Bland’s refusal to put out a cigarette seemed excessive.