Dozens of videos, court documents, autopsies and police reports reviewed in these cases — involving a range of people who died in confrontations with officers on the street, in local jails or in their homes — show a pattern of aggressive tactics that ignored prevailing safety precautions while embracing dubious science that suggested that people pleading for air do not need urgent intervention.

The study noted that often what leads to suspects choking to death while being detained is police officers’ assumption that they’re lying or exaggerating when they complain that they can’t breathe.

The study’s findings suggest that in nearly half the cases, the detainees “were already at risk as a result of drug intoxication” and some had underlying health issues, but that really doesn’t matter because, as the study suggests, the issue isn’t just why detainees were having trouble breathing, but how officers responded (or didn’t) when their suspects told them they couldn’t breathe.

The Root also reported the case of Javier Ambler, a black man who repeatedly told police officers, “I have congestive heart failure.

Then last week, the Police Department in Tucson, Ariz., released video of an encounter on April 21 with Carlos Ingram Lopez, who was naked and behaving erratically when officers forced him to lie face down on the floor of a garage with his hands handcuffed behind his back.