What is a chokehold?
It's when you grab a person from behind, wrap your arm around their throat tightly and cut off the flow of blood and oxygen to their brain.
How deadly is it?
Chokeholds are dangerous, especially - as in the case of Eric Garner - if the person being grappled has health issues.
A 1982 paper in the American Journal of Forensic Medicine and Pathology states that, in a chokehold, the victim's "struggle to free himself only increases the force around the neck.
"The desire to free himself intensifies and increases the pressure."
Between 1975 and 1982, when police more often used the chokehold, 15 people were killed.
Are US police allowed to use it?
There is no federal law preventing police from using a chokehold.
Already allowed to use force when they fear for their life or are making an arrest, US police officers' right to use the chokehold is fortified in 1989 when the Supreme Court ruled that an officer's decision in the heat of the moment is beyond reproach.
In New York City, in particular, the chokehold is banned. It was first regulated in 1985, and then outright banned in 1993 after an officer killed 21-year-old Federico Pereira.
If the NYPD has banned it, why isn't Officer Daniel Pantaleo being charged?
Despite the fact that the incident was caught on film, and Eric Garner was not particularly combative, a New York City grand jury didn't want to press charges.
People are understandably dismayed by this decision, and have taken to the streets of Manhattan to protest it.
But Pantaleo was never likely to be indicted, because that would be almost unheard of for a police officer in the field.
Josh Voorhees of Slate said: "Nearly everyone involved in the system is willing —perhaps even eager — to believe that an on-duty officer who takes another citizen’s life was justified in doing so.
"Police officers get that benefit of the doubt at every step along the way."
And this can be brought back the 1989 Graham v Connor Supreme Court ruling - don't second guess a cop.
But it's not quite over, with US Attorney General Eric Holder announcing that the Department of Justice will investigate possible civil rights violations to the Garner case.
What's the racial angle to this?
In the wake of what's happening in Ferguson, Missouri following the death of Michael Brown at the hands of a police officer, the question of race is especially potent.
Eric Garner's widow, Esaw is reported to have likened his killing "to a modern day lynching."
Back when the manoeuvre was commonly used by police - 975 times in an 18 period around 1982 - black people were disproportionately the victims.
12 of the 15 killed by police chokehold between 1975 and 1982 were African American.
At the time, NAACP representative Jose De Sosa told the Sentinel: "Black men are subject to die from strangulation or ‘chokeholds’ as they call them four times more than white men"
Even the cops spotted it, with then Los Angeles Police Chief Daryl Gates launching a well-meaning but flawed investigation into why more African American were being asphyxiated by police - thinking they may be more physically susceptible.
The Washington Post's Morning Mix say the chokehold is "racially charged".Reuse content