Eric Garner death: What next for the chokehold?
A New York city police officer will not face trial over the death of Eric Garner, an unarmed man who died after police tried to arrest him for selling loose cigarettes.
But what about the tactic used to restrain him?
What is a chokehold?
The chokehold has long been considered a controversial technique for law enforcement officers in the US, although it's not a term widely used in other countries such as the UK.
Video footage of the incident shows officer Daniel Pantaleo lock his arm around Mr Garner's neck, before wrestling him to the ground.
"As defined in the department's patrol guide, it would appear to have been a chokehold," New York City Police Commissioner Bill Bratton told reporters at the time.
It is defined in the New York Police Department patrol guide as any pressure to the throat or windpipe that may hinder breathing or reduce intake of air.
They have been prohibited in New York since the 1980s because, in Bratton's words, of the "concerns of potential deaths around them." Most police departments across America also ban their use.
Choke or strangle?
The origins of the chokehold come from martial arts such as judo, where it is also known as a "shime waza", explains Gary Golz, president of the US Judo Association.
Mr Golz, who has been a defensive tactics adviser for the Los Angeles Police Department, says there are several iterations of the chokehold, which he describes as more of a strangle than a choke.
"If they choke, you're doing it wrong," he says.
Mr Golz says the move applies pressure to the carotid artery in the neck, restricting blood flow to the brain. "It should be a very painless hold, it would knock you out, and make you feel kind of woozy, then you'd be fine."
In judo this move would only last between 3-15 seconds, says Mr Golz.
"After that it's going to take on a new dimension, the person is going to pass out... go longer, [for example] a minute or two and someone could die."
Golz believes it can be a very effective move for officers to restrain people, as long as they are trained properly.
"Problem is lots of police don't have the skills that a judo person who's been doing it for 5-10 years has".
Is the chokehold widely used by police?
Even though police officers in New York aren't meant to use the move, many still do.
A report released in October 2014 by the New York City Civilian Complaint Review Board (CCRB) said 1,128 complaints about chokeholds had been received in the past five-and-a-half years.
Between July 2013 and July 2014 there were 219, the report said, with the vast majority of chokehold cases occurring with more than one officer present.
The report said the NYPD was failing to appropriately discipline officers because of inconsistencies in how they interpret what a chokehold is.
In judo terms the definition may be simpler, but the CCRB report says in the NYPD there is an "interplay" between pressure and breathing tests for chokehold complaints.
"For some investigators, a chokehold existed if and only if breathing was restricted, while for others, it was correctly, the presence of pressure regardless of whether breathing is restricted," it noted.
What next for the chokehold?
The New York medical examiner concluded that a chokehold played a part in Eric Garner's death, but there are others who dispute that.
Pat Lynch, president of the patrolmen's benevolent association (PBA), a union which represents officers in the city, says Officer Pantaleo did not use the tactic, and "was bringing a person to the ground the way we're trained to do to place him under arrest."
The PBA says it is saddened by Eric Garner's death, but that the officer's intention was "to do nothing more than take Mr Garner into custody".
Retired NYPD Detective Sergeant Mike Codella who runs a Ju-Jitsu academy in Staten Island teaching chokeholds to clients including police officers, believes they should not be banned.
"In the force the idea is to match the force being used against you. If your life is seriously in danger you have to use whatever technique to defeat the person who is on the attack.
"It should be used the way a gun is used - you wouldn't fire a weapon at a person if you don't feel your life is in danger. You have to use minimum amount of force to win the situation."
The CCRB report calls for NYPD officers to be trained to use alternative methods for restraining suspects, as well as reaching an understanding on what is considered appropriate and even-handed discipline.
The NYPD has already announced it will be retraining 36,000 officers on guidelines and tactics on the use of force following Eric Garner's death.
This case has further inflamed an ongoing national debate about the use of police force, and the extent to which it should be used.
It follows the recent decision by a grand jury not to indict police officer Darren Wilson for shooting unarmed teenager Michael Brown in Ferguson, Missouri.