Image copyright Getty Images Image caption Mike Bloomberg (L) was criticised by Bernie Sanders for his record as New York City mayor

Mike Bloomberg's record as mayor of New York City and his support for the controversial stop-and-frisk policy was a huge talking point in the Democratic Party presidential candidates' debate last night.

We've been fact-checking some of the claims.

What is stop and frisk?

Stop and frisk, similar to stop and search in the UK, is a police tactic to reduce violent crime. It gives police officers powers to stop someone they suspect of committing a crime and the authority to search a person if they are suspected of carrying a weapon.

Claim 1: Mike Bloomberg said: "I discovered that we were doing many, many, too many stop and frisks. We cut 95% of it out."

Reality Check: The billionaire businessman was mayor of New York from 2002 to 2013 and during these years he expanded the use of stop and frisk.

Mr Bloomberg had defended this policy as recently as October 2019. Then in November, a week before he launched his presidential bid, he apologised for it. In last night's debate, he said it "got out of control".

It's true there was a big reduction in the number of times stop and frisk was used by police towards the end of his tenure after it had peaked in 2011.

However, prior to that stops had grown by more than 700% since Mr Bloomberg became mayor in 2002.

For the 95% figure, he appears to have picked quarterly data from the first quarter of 2012 compared with the last quarter of 2013 when numbers dropped from 203,500 to 12,485.

Image copyright Getty Images Image caption Police officers in New York City carried out about five million stops during Mr Bloomberg's three terms in office

Claim 2: Mr Bloomberg said he successfully reduced the crime rate in New York [we think he meant number of murders] "from 650, 50% down to 300".

Reality Check: The number of murders in New York City dropped by half during Mr Bloomberg's administration, and the number of major crimes also dropped substantially by more than 45%.

Was this due to the stop-and-frisk policy?

City officials have argued it was key to reducing the city's crime rate.

However, a study by the Department of Criminology at the University of Pennsylvania says stop and frisk "made almost no difference" to crime reduction, and instead cited the increased police presence in high crime neighbourhoods as a major factor.

The numbers show that both murders and overall major crime continued to drop from 2013 onwards when stop and frisk was substantially reduced and after Mr Bloomberg left office.

More than 87% of people stopped and frisked during Mr Bloomberg's time as mayor were innocent and around 1.5% of searches found a weapon.

Claim 3: Bernie Sanders suggested stop and frisk targeted minorities and "went after African American and Latino people in an outrageous way".

Reality Check: Almost 90% of those stopped during the Bloomberg era were African American or Hispanic (and this continues today).

These two groups combined made up around 50% of the New York City population, according to 2010 census data.

Defenders of the policy deny there was targeting and say stops were based on the description of suspects or suspicious behaviour.

In 2013, a New York judge ruled the programme was unconstitutional and ordered it to be reformed.

The ruling contained the following details:

Half of all the stops were followed by a search of the person. A weapon was found after 1.5% of searches

Weapons were found on 1% of the African American people stopped, 1.1% of Hispanics, and 1.4% of white people

Claim 4: Joe Biden said stop and frisk led to "throwing close to five million young black men up against a wall".

Reality Check verdict: This isn't true. There were about five million stops recorded by police during Mr Bloomberg's terms in office. But as we've shown, about half were of African Americans.

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