Over the years, reports of brutality and neglect at the Rikers Island jail complex have become routine. And while the administration of Mayor Bill de Blasio has been working to improve conditions at New York City jails, the death of Carlos Mercado shows that the problems of the past could haunt the city for years to come.

On June 22, 2013, Mr. Mercado was arrested in Brooklyn after allegedly trying to sell a small amount of heroin to an undercover police officer. He was taken to Rikers and, within 15 hours, died of complications of diabetes.

In this jail surveillance video obtained by The New York Times, he is seen walking unsteadily and carrying his vomit in a plastic bag. At one point he collapses on the floor and is left lying there for three minutes while correction officers step over him. Rankin & Taylor, a law firm representing Mr. Mercado’s family, is in settlement negotiations with the city.