The police watchdog is launching a review into whether police tactics, such as stop and search, discriminate against ethnic minorities.
It comes after the Metropolitan Police apologised to Team GB athlete Bianca Williams and her partner, who were pulled out of their car to be searched.
What is a stop and search?
In England and Wales, stop and search is the power given to police to search an individual or vehicle if they have "reasonable grounds" to suspect the person is carrying:
- illegal drugs
- a weapon
- stolen property
- something which could be used to commit a crime, such as a crowbar
Police officers cannot stop you because of your race, gender or any previous criminal record.
Instead, they must assess the situation based on current intelligence (for example, has there been a local robbery?) and on behaviour that - on balance - is suspicious.
But what counts as "reasonable grounds" has sometimes been controversial.
In 2017, police chiefs argued with the College of Policing - which sets guidance for police officers - after it said that the smell of marijuana alone did not always justify a stop and search.
What rights do you have?
You must comply if stopped by the police.
However, they should also tell you:
- Why they are stopping you and under what law
- What they expect to find on you
- A receipt of the search, or information on how to get one
An officer can ask you to remove gloves, a jacket or coat.
However, if they want to remove anything else (including religious clothing) they must take you out of public view. You should also be searched by someone of the same sex if this happens.
You are able to record a stop and search, but this must not obstruct it. Many police officers also have body cameras.
If you have a complaint about the search you should be given contact details from the officer, or find them online.
How many stop and searches are there?
Stop and search has decreased considerably since its 2009 peak, when 1.5 million took place in England and Wales.
That coincided with the Metropolitan Police's Operation Blunt II, which tackled knife crime in London, a scheme supported by then city mayor, Boris Johnson.
Last year there were 380,000 searches, the first year-on-year increase in a decade.
However, with knife crime increasing in recent years, some, including now Prime Minister Mr Johnson, have argued that it should be considered as a key way to tackle the rise.
What about Scotland and Northern Ireland?
For example, reasonable grounds are needed for most searches and there are a number of rules that the police must follow.
In 2018-19, there were 41,167 stop and searches in Scotland and 25,540 in Northern Ireland.
Is stop and search racist?
A black person is nine times more likely to be stopped and searched than a white person.
Stop and search was mentioned as a key cause of tensions in reports after the 1981 Brixton riots and the racist murder of Stephen Lawrence.
The inquiry into Mr Lawrence's murder led to the Metropolitan Police being labelled "institutionally racist". The debate on police practices and culture which followed led to better recording practices on ethnicity and stop and search.
MP David Lammy's 2017 review of police and courts' treatment of black and minority ethnic groups (BAME), said those communities felt the justice system remained "stacked against them", with stop and search at the forefront.
Does the evidence back their use?
A number of stop and search reports have questioned its impact, including ones commissioned by the government.
A 2016 Home Office report into Operation Blunt II concluded that the tactic's widespread use had "no discernible crime-reducing effects", but did suggest that there could be greater impacts locally.
In 2018, the government's Serious Violence Strategy made similar conclusions.
In the same year, College of Policing found higher rates of Metropolitan Police stop and searches only slightly decreased crime immediately afterwards.
Another way to measure stop and searches is by how likely they are to lead to an arrest.
Since 2014, the proportion of stop and searches resulting in an arrest has doubled.
But overall, the amount of arrests has dropped - it has become more effective in one way, but produced fewer overall arrests.
It's worth pointing out though that not all searches where something is found will always result in arrest, such as small-scale drug possession.
Do they always require "reasonable grounds"?
The majority of stop and searches are carried out under Section 1 of the Police and Criminal Evidence Act, which requires "reasonable grounds."
However, 4% of stop and searches are so called "Section 60s" and do not require this level of suspicion.
A Section 60 can only happen in a set area (normally a neighbourhood or, sometimes a whole borough) for a set period of time. It must be approved by a senior police officer when there is a belief that a serious crime has been, or is about to be, committed.
These Section 60s see lower arrest rates and target black people more.
Recently, Mr Johnson reduced the threshold on the seniority of the police officer who can authorise a Section 60. However, their use was already increasing before that.