The family of an 18-year-old black woman who died in police custody in Alabama are demanding to see video footage taken inside the jail cell where she was held for several hours before she was discovered lifeless.

Sheneque Proctor, the mother of an infant boy, died in a holding cell at Bessemer city jail on 2 November. She had been arrested the previous afternoon for alleged disorderly conduct and resisting arrest outside a private party she was attending with friends.

In their first media interview, members of the Proctor family told the Guardian that questions over Sheneque’s death have gone largely unanswered by city and state officials. They suspect neglect on the part of her jailers, and see her passing as the latest example of unequal treatment of African Americans in the hands of US law enforcement.

The dead woman’s mother, Scherita Proctor, said that in her opinion the jail had failed to give her daughter medical help at a critical – and ultimately fatal – moment. “I don’t think she was treated fairly. She may have acted out, but that doesn’t mean you refuse to help her.”

She also complained of the lack of information coming from official sources. “I don’t feel I’ve been given any respect, considering I lost my child. They should have at least have come to me and told me something.”

The family’s lawyer, Hank Sherrod, who has experience of cases of death in police custody, said that the city police department had promised to release the video to the family by the New Year but had so far failed to honour the pledge. “This young woman was denied medical treatment while being recorded on videotape right before police eyes. The fact that they won’t hand the film over makes us wonder what they have to hide.”

A rally is being organised on Saturday morning by the Alabama branch of the NAACP outside Bessemer city jail. A petition has also been launched on change.org that calls for a federal investigation into Proctor’s death.

Sheneque Proctor and her son Zamaruien Blevins. Photograph: Proctor family

“All over the country, African Americans are treated as though they are guilty by law enforcement. Here in Alabama, black people don’t receive equal treatment when they’re arrested,” said Benard Simelton, president of the Alabama state conference of the NAACP who is advising the Proctors.

At the time of her death, Sheneque Proctor had just turned 18. She graduated from Pleasant Grove high school last May and had given birth to her first child, Zamaruien Blevins, in July.

On 1 November she went to a party at an Economy Inn in Bessemer, to which police were called following a reported disturbance. In a phone conversation with her mother after her arrest, Proctor said that she had been roughly handled by three police officers who slammed her against a police car, handcuffed her and then threw her into the back seat of the vehicle.

“Mama, come and get me,” Scherita Proctor recalls her daughter saying to her.

Arriving at the jail, Proctor was pepper-sprayed by officers after “slipping out” of her handcuffs at least twice, according to official documents. This official narrative states that she was booked into the jail at 2.39pm on 1 November, then decontaminated from the pepper spray before being put into the holding cell where she remained overnight, kept under observation approximately every half-hour with the last observation taking place at 3.37am.

During the night she was heard “snoring loudly” in the cell. At 4am an officer brought a breakfast tray for her but found her unresponsive on the bed. Paramedics were called and after an attempt at resuscitation she was pronounced dead at 4.40am.

A postmortem was conducted on the day of her death. The autopsy report noted that “clear froth was observed coming from her mouth”; it also recorded that she had a history of asthma.

Toxicology tests on her blood recorded the presence of the heroin substitute methadone, cocaine and the anxiety-inhibiting drug Alprazolam. Though no alcohol was found, trace elements of a metabolite suggested she had earlier been drinking.

The medical examiner concluded that Proctor’s death had been an accident caused by “complications of polydrug overdose”. The Guardian contacted an independent forensic toxicologist who confirmed that the combination of drugs in her blood at the levels recorded could have been sufficient to cause death.

Nathaniel Rutledge, the Bessemer city police chief, said there was no evidence that Proctor had been mistreated or neglected. “No one wants to hear of their child dying like that, but that’s what they found – she is another victim of heroin.”

Rutledge insisted that the department treated citizens “fairly and equitably. We give the best service that we can and there’s no discrimination by race.”

Sheneque Proctor. Photograph: Proctor family

Asked whether the video footage would be released to the Proctor family, he said that the decision would be made by the district attorney once an inquiry into the death had been completed by the state bureau of investigation.

For the Proctor family, though, a slew of questions remain. Was she properly decontaminated from the pepper spray, particularly given her chronic asthma? Did Proctor’s “loud snoring” before her death indicate breathing problems that should have been detected and treated? How frequently did officers check on her, given that the family has not been allowed to see the official observation file? With no criminal proceedings pending, why hasn’t the video been released?

“There are more questions than answers here. Until we see the video, we won’t know for certain what happened to her in the jail,” Sherrod said.

Had Proctor’s deteriorating condition been detected earlier, there is a chance that her life could have been saved. Experts in the prevention of overdoses say that numerous treatments are available to paramedics, including the drug Naloxone to counteract methadone, CPR, mouth-to-mouth resuscitation, intubation or ventilation.

“There are many life-saving measures that can always be tried,” said Meghan Ralston, harm reduction manager for the Drug Policy Alliance. “They may not work 100% of the time, but there are things that can be done.”

Two months after Sheneque Proctor died, her family is still waiting to be given back her possessions. “We want the police department to know that we aren’t satisfied by the lack of response,” Simelton said.

Sheneque’s uncle, Donnell Sanders, said that as a military veteran with 30 years’ public service he has no animus towards the police. But he said that the authorities had shown “no sympathy, no passion since my niece’s death. That is neglect, and I don’t understand it at all.”

Sanders said he is painfully aware that the family will eventually have to explain to Zamaruien, now six months old, why he has no mother. “It will be our job to tell him that she passed away in a police cell. And then it will be our job to help him grow up to be a positive young man, and not one paralysed by paranoia, fear and anger.”