A controversial US police chief has been hired by the government of Bahrain to train and reform the nation's security forces.

John Timoney spent nearly three decades with the New York City police department before serving as head of police in Philadelphia and Miami. He's been hired – along with former assistant commissioner of Britain's Metropolitan Police, John Yates – to reform Bahrain's security forces. The two were brought on after a report was published detailing the torture and death of prisoners held by Bahraini authorities.

Timoney's supporters view him as a tough, smart cop with a record for turning failing police departments around and controlling mass demonstrations. In effect, they argue, he's the perfect candidate to improve Bahrain's security forces, which have been linked to the killing, torture and flagrant suppression of dissident protesters.

The chief's critics, however, say Timoney's handling of protests and gatherings in each of the cities he's served in are wrought with examples of police abuse, illegal infiltration tactics, fear-mongering and a blatant disregard for freedom of expression.

News of Timoney's appointment in Bahrain first broke in December. In an interview with NPR, Timoney was asked whether the people of Bahrain have a right to protest.

"On a daily basis, they absolutely have the right to protest, to demonstrate," Timoney explained. "Here's where the problem comes in. It's a small city. It reminds me more of lower Manhattan than the rest of Manhattan, where you've got these narrow streets."

He warned of the dangers of unauthorized marches impacting traffic.

"When you saw Occupy Wall Street, when people begin to engage in unauthorized marches that begin to cripple traffic and emergency vehicles," Timoney said. "There's a reason why you have to go to the police department. It's not that they say, yea or nay regarding your right to speech, but can this be handled that it doesn't dramatically and drastically impact the rest of society?"

One day later, Bahrain's ministry of interior picked up on Timoney's traffic narrative, tweeting: "Groups marching from Budaiya Rd to SH Khalifa bin Salman Rd have blocked traffic. Police are dealing with the situation."

Timoney went on to tell NPR that, of the protests he had so far witnessed in Bahrain, police had given protesters "proper notice" and kept a distance between themselves and a crowd.

As recently as Tuesday, the one year anniversary of Bahrain's uprising, protesters were clashing with police in the nation's streets. According to the BBC, "a massive police and army presence" was in effect in the capital city of Manama, leading to a largely quiet scene. In the outskirts of the capital, however, police reportedly shot tear gas and rubber bullets at demonstrators, who responded by tossing petrol bombs and stones at the authorities. A doctor who spoke to the BBC said the security approach in her country had become "more severe" since last year.

Bahraini security forces in Manama during clashes with protesters. Photograph: Mazen Mahdi/EPA

The use of tear gas has been a particularly contentious issue in Bahrain's protest crackdowns. According to Amnesty International, Bahraini human rights groups have reported at least 13 deaths resulting from the use of tear gas since the protests began last year. At least three of those deaths occurred after Timoney was hired, and include Salma Mohsin Abbas, 81, and Yaseen Al Asfoor, 14, who reportedly died after canisters were set off in their homes. Sayyed Hashem Saeed, 15, meanwhile, died on December 31 after being hit with a canister at close range.

While it is unclear whether Timoney has advised Bahraini authorities in their use of tear gas, his reliance on the tactic – as well as other less-lethal implements – was on full display during the end of his policing career in the United States.

Timoney's first notable involvement in a large scale clash between the police and the public occurred in 1988, when he was deputy commissioner of the NYPD and led the response to the so-called Tompkins Square Park riot. The incident resulted in 121 complaints of police misconduct and helped launch Timoney's reputation as an officer who could deal with large crowds. That same year he was brought on as commissioner of the Philadelphia police department.

As commissioner in Philadelphia, Timoney presided over the arrests of more than 380 protesters at the 2000 Republican National Convention. At the time, the ACLU's Philadelphia chapter denounced Timoney's department for collaborating with the state police to infiltrate and spy on protest groups, in violation of a mayoral decree. Before the protests began Timoney's officers conducted raids of warehouses and spaces where activists where constructing puppets and banners for the demonstrations. That same year Esquire magazine called Chief Timoney America's "best cop" and praised his rough and tumble attitude, as well as his commitment to protecting the public.

John Sellers was in Philadelphia at the time. While he had trained activists during the days leading up to the convention, Sellers says he was in Philadelphia as an "observer" and was "in no way involved with the actual protests".

That didn't stop the police from arresting him on 13 misdemeanor charges, including "possession of an implement of crime." In this case the "implement" was his cellphone. His bail was set at an unparalleled $1m. At least two other demonstrators had bails set at $500,000.

"The Philadelphia police were very aggressive. They operated covertly and went undercover, posing as protesters and posing as ordinary people who were upset with the Republican agenda," Sellers told the Guardian.

In Philadelphia Timoney's officers favored a hands-on approach to managing demonstrators. Sellers explained, "It was much more of an up close and personal, beat-you-down kind of violence in the streets. Cops were smashing people with bicycles and nightsticks."

Kris Hermes was part of the legal support team in Philadelphia during the RNC in 2000. He later joined the legal collective that worked with activists in Miami when Timoney cracked down on the Free Trade Area of the Americas summit in November 2003. He is currently writing a book about the years he spent providing legal support work for the hundreds of cases that resulted from Timoney's legacy in Philadelphia. Hermes has tracked the shifts in Timoney's career and their impact on police tactics.

"I think Philadelphia represented the beginning of a shift in policing in the United States and I think Timoney was responsible for that. And what he learned in Philadelphia he took to Miami and expanded on it," Hermes told the Guardian.

"It wasn't until Miami that there was really a whole panoply of weaponry that was used against protesters," Hermes added.

When Timoney took on the role of Miami's police chief in December 2002, his methods for dealing with mass demonstrations had evolved to include the use of pepper spray, rubber bullets, bean bag rounds, Tasers, electrified shields and batons. The tactics were on full display during the Free Trade Area of the Americas summit protest.

The documentary The Miami Model depicts several scenes in which police in riot gear are seen shooting non-violent demonstrators with "less-lethal" rounds, hitting protesters with fists and batons and using Tasers extensively. The film-makers also interviewed several anonymous local residents who say the police encouraged them to rob legal observers and people involved in the protests.

One Florida judge on the ground during the crackdown said in open court that he had personally witnessed at least 20 felonies committed by police officers under Timoney's command. The ACLU received 150 complaints of police abuse and filed over a half dozen lawsuits on behalf of protesters in federal court.

Before and during the protests in Miami Timoney made a concerted effort to control the narrative, both in the media and in the community. Under Timoney, police reportedly used photos from the the 1999 WTO protests in Seattle to influence local business owners.

"There was a big effort in downtown Miami where the protests were set to occur to scare business owners by showing them images of Seattle, as though that was going to happen again," Hermes noted. Additionally, officers would arrest activists for gathering in groups larger than seven and for handing out literature detailing their reasons for protesting.

Each day during the Miami protests the police would deploy dozens of "embedded journalists" – mostly reporters from mainstream outlets – in flak jackets and helmets with local law enforcement. The reports that were filed often resembled correspondences from Iraq or Afghanistan, and tended to downplay the issues being protested in favor of focusing on police efforts to combat anarchists. The department said it could not guarantee the safety of journalists who did not embed.

Police in Miami during the Free Trade Area of the Americas meetings in 2003. Photograph: Andrew Gombert/EPA

Indeed, many journalists were hurt and arrested in Miami. Independent film-maker Carl Kessler suffered nerve damage when a bean bag fired by police struck him in the eye. The injury ultimately resulted in a $180,000 settlement. Ana Nogueira, a reporter with the independent news program Democracy Now!, was arrested and forced to strip naked in front of male police officers because her clothing was soaked in pepper spray.

Despite the numerous criticisms, Howard Simon, executive director of the ACLU in Florida, is quick to point out that Chief Timoney oversaw significant improvements in the culture of the Miami police department.

"I think he was probably one of the most professional, competent and experienced police chiefs the city of Miami ever had," Simon told the Guardian.

Timoney arrived to Miami when the department was in a "state of crisis", Simon explained. At the time a dozen Miami police officers had been federally indicted in the shootings of multiple unarmed, young African American men. Simon recalled a period of "about 22 months" following Timoney's arrival in which there was not a single incident of a police officer discharging his or her weapon.

"He changed the culture from the top down in the Miami police department," Simon pointed out. "And then he left and, lo and behold, there were seven killings within a period of seven months."

Still, Simon acknowledges that his organization filed no less than seven lawsuits against Timoney and his department for "the squelching of first amendment rights during the 2003 Free Trade Area of America agreement meetings that took place in Miami."

"He had a difficult job of trying to balance both the needs of safety and the need to protect constitutional rights, and I think in that respect in November of 2003 he failed," Simon said. "In an honest moment I would like to think that he acknowledges that. It got away from him."

Hermes believes Timoney's perceived success in certain areas of law enforcement does not absolve him of his history in handling mass demonstrations, "Even if his record was good outside of the context of political protests, definitely within the context of political protests he is abysmal."

Hermes describes Timoney's appointment in Bahrain as "extremely unsettling".

"I'm concerned for the people of Bahrain with Timoney directing how police there are controlling crowds," Hermes added. "I think his reputation, unfortunately, gives him a lot more credence than he deserves."