Footage of the 10 July arrest shows Sandra Bland’s car being pulled over for failing to signal and then an ensuing confrontation with the officer.
There are several jumps during the 52-minute film, which has had more than one million views on YouTube.
But Texas authorities say it was not edited and that it will be re-uploaded.
The coroner said the 28-year-old hanged herself in her cell but her family has demanded an independent post-mortem examination.
State officials and the FBI are both investigating her death.
In the video, released by the Texas Department of Public Safety (DPS), Brian Encinia, a white police officer, is seen issuing a ticket and then asking her to stub out her cigarette, which she refuses.
When she refuses to step out of the car, he tries unsuccessfully to pull her out. He then appears to threaten her with a Taser and says the words: “I will light you up.”
She gets out of the car and they move out of vision, but the audio suggests the confrontation becomes physical before more officers arrive.
Several breaks in the video were highlighted on social media shortly after the film was released with many using the broken footage to question the entire film’s authenticity.
In a statement released on Wednesday, DPS spokesman Tom Vinger said the video “has not been edited”.
“Some of the video… was affected in the upload and is being addressed. We are working to repost the dashcam video,” he added.
Video inconsistencies
- 25:01 – A man walks away from a pick-up truck and out of shot, before reappearing at the door of the vehicle a few seconds later
- 32:37 – A white car comes into shot then disappears before reappearing a couple of seconds later. The audio doesn’t appear to break during this time, with the officer heard discussing the incident
- 33:04 – The same footage of the white car is looped, again with no noticeable break in the audio
Officer Encinia, who has been on the force for just over a year, said he was kicked during the arrest. He has been put on administrative leave.
Texas DPS director Steven McCraw said his officers have “an obligation to exhibit professionalism and be courteous” but that “wasn’t the case in this situation”.
‘Heavily disproportionate’
Prof Lawrence Sherman, director of the Institute of Criminology at Cambridge University, said the video clearly shows the officer is “out of control”.
He told the BBC that the response was “heavily disproportionate to the seriousness of the offence” and that he believed “a suit against [Mr Encinia] for illegal arrest would be very successful”.
The debate about authenticity of the arrest video was a sign of the distrust towards police in the US, Mr Sherman added.
Authorities also released surveillance video from the jail showing officers responding to Bland’s death but it does not show the cell.
Jail Sheriff Glen Smith said his staff checked on Bland less than an hour before she was found dead.
In March, Bland said she was suffering from “a little bit of depression” and post-traumatic stress disorder in a video posted on her Facebook page.
But family and friends say she was in good spirits in recent months and had just started a new job. She was also said to be in good health when she arrived at the jail.
Her death is one of several under scrutiny in the US in which a black person has died while in police custody.
Other high-profile cases, since the death of Michael Brown in Ferguson last summer, have sparked protests and sometimes unrest.
On Tuesday prosecutors in Cincinnati, Ohio, said they were probing the fatal shooting of a black motorist by a white police officer who had stopped him over a missing licence plate.
Samuel Dubose apparently refused to co-operate with Officer Ray Tensing, leading to a struggle.
Dubose, 43, was then shot in the head and pronounced dead at the scene.
The police officer has been placed on paid administrative leave while the investigation continues.
“When she refuses to step out of the car, he tries unsuccessfully to pull her out. He then appears to threaten her with a Taser and says the words: “I will light you up.”
It was at this point that a gun could have saved her life.
Of course they would deny it. What do you expect from criminals? The truth?