By Jason Farrell, Senior Political Correspondent, Sky News

A new app is being launched to help members of the public capture incriminating footage of police confrontations with civilians.

British civil rights campaigners got the idea on a recent visit to California, where they met members of the Black Lives Matter movement, which campaigns against race-related police brutality.

The US version of the app, created by the American Civil Liberties Union (ACLU), is "designed to help people hold the police to account".

It allows people to film the police and send the footage to ACLU where it can be assessed by lawyers.

In California, 170,000 people have downloaded the app since it was launched six months ago.

US App 'To Hold Police To Account'

Demand for the US version of the app has grown

The UK app has been developed by the charities Release and Stop Watch and will also use lawyers to assess footage.

Among the UK activists visiting California was Shaun Hall, the brother of Mark Duggan who was shot dead by police in 2011, sparking the London riots.

Freddie Gray

Video: APR: Video Of Freddie Gray's Arrest

Mr Hall and the Caravan For Justice group are now looking to promote a similar app called YStop in the UK.

He told Sky News: "I've heard instances where the police have been filmed; they actually go and take the phone and maybe even damage the phone or delete what's been filmed.

"The brilliance of this is that as soon as you press send it is gone."

Ade Johnson, whose brother-in-law Sheku Bayoh died after being restrained by police in Fife in May, said: "Sometimes witnesses are scared to come forward and show the footage that they've got.

"They don't want to go to court and so on. If there is an app that they can use to just forward what they've seen or what they've recorded, we welcome that."

Mobile phone footage of police has caused controversy in the US - notably the relentless beating of Rodney King which was filmed in 1991 and led to riots after the officers involved were acquitted of wrongdoing.

More recently video filmed in April showed the arrest of Freddie Gray in Baltimore as he was dragged into a police van.

He later died of a broken neck and six police officers have been charged in connection with his death.

Baltimore is where the US app is being launched next.

Meredith Curtis, from the Maryland branch of ACLU, told Sky News: "We have had cases in the past where police have seized people's phones and wiped the recordings. This stops that from happening.

"The ACLU stores the videos and our app also prompts you to complete a witness report that can be viewed by our lawyers.

"We have hundreds of activists and concerned citizens wanting to get hold of the app, so they can use it to hold the police accountable."

The Black Lives Matter movement has grown since the shooting of Michael Brown in Ferguson last year.

However, police warn "the Ferguson effect" has led to increased aggression towards officers.

Recent FBI figures show 48,000 police officers were attacked last year, and 51 were killed by offenders.

FBI director James Comey has argued that crime has risen as a result of police becoming more timid.

Murder rates in Baltimore for example are up 56% with over 100 homicides in the last three months.

James Pasco, executive director of the Fraternal Order of Police, told Sky News: "Arresting people is not pretty and if something causes them to hesitate at a point when they ought to be moving instinctively, consistent with their training, then that could have disastrous effects."

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