This is the second post in a series considering the contentious but increasingly relevant issue of recording police interactions. In this series, we offer up some case-study examples where surveillance cameras have been used as a force for good.

We've often commented on the double-edged nature of persistent surveillance. On the one hand, constant surveillance can lead to various privacy and civil liberties abuses. But as the following stories show, widespread adoption of surveillance cameras by both law enforcement actors and civilians can also help hold both parties accountable.

While cops have had mixed reactions to recording their interactions with civilians, many police departments have begun to adopt in-car and wearable video camera technologies. For example, The London Metropolitan Police Service (MPS) recently announced a one-year pilot project that equips cops with body-worn video cameras to be used during their interactions with the public. Likewise, across the pond, the Boston and Los Angeles Police Departments have installed self-monitoring systems on police cruisers. Dozens of other US police departments, including those in Fort Worth, Las Vegas, and New Orleans, have deployed wearable police cameras.

"Video captures events in a way that can't be represented on paper in the same detail, and it has been shown the mere presence of this type of video can often defuse potentially violent situations without the need for force to be used," MPS Commissioner Sir Bernard Hogan-Howe explained in a press statement upon rolling out the new police camera initiative.

According to a study conducted by the Rialto, California Police Department, after wearable video cameras were introduced to the town's police force in February 2012, public complaints against officers plunged 88 percent compared with the previous twelve months, and officers' use of force fell by 59 percent. This despite officers' increased interactions with the public compared to the previous year, according to the study.

The following examples are a few situations where video (or audio) footage surfaced showing police officers' actions to have been justified in light of the circumstances.

Pissed off

Background: A 19-year-old, "really heavily intoxicated" man was arrested last year outside the Beats Night Club in Queensland, Australia, after Queensland Police Union (QPU) officers responded to a call that he was urinating at the establishment's front door. A video recording of a portion of the arrest was taken by a civilian at the time and was later posted to the Internet, according to the Brisbane Times.

What the complainant argued: While the man was in the process of launching a formal complaint against the officers, the QPU received a significant amount of hate mail stemming from what appeared to be their improper use of force, based on the images reproduced in an edited video portion of the arrest released on the Web. The letters criticized the officers for kicking the man and striking him with unnecessary force, some of which referred to the officers as "thugs." The incident also precipitated an Ethical Standards Command committee review, explains the Brisbane Times.

What the cops said: The cops involved argued that the edited mobile phone footage posted to the Web did not provide a full enough picture of the circumstances, and that the officer who appeared to kick the man was, in fact, simply trying to spread the man's feet apart in order to properly cuff and restrain him. What's more, the officers argued that their use of modest force was justified and appropriate in light of signs that the drunk man appeared belligerent and as if he was about to either strike and/or spit on the them.

What the unedited video showed: QPU President Ian Leavers explained that independent CCTV footage of the arrest showed that the officers acted appropriately in defending themselves against the teen. "[He] clenched his fist, pumped his chest out, started to lick his lips and come towards police," Leavers described of the events as seen on the surveillance camera footage. "Police with an open hand have pushed him in the center of the chest, not with a fist...pushed him back and restrained him... Police have now been vindicated, [the CCTV footage] shows their actions were appropriate, lawful and they acted in a professional manner at all time," Leavers continued, reports the Brisbane Times.

Split second decision

Background: While Pittsburgh officers were patrolling a crime-ridden area of town late one night in April 2014, they spotted a gun in plain view inside a parked Chevy Malibu car. Once a man named Adrian Williams returned to the vehicle in question from the Serenity night club at 3am, officers turned on their sirens to pull him over, after which a high speed car chase ensued. Williams then proceeded to crash the car and flee on foot with gun in hand. While two officers chased Williams on foot, another pulled up in his cruiser and captured video of an officer shooting and killing Williams, reports the Pittsburgh Post-Gazette.

What the video showed: Video footage taken from the police cruiser showed Williams fall onto the ground as he was fleeing by foot, roll over, and point his gun at Officer Christopher Kertis. While the Allegheny County District Attorney Stephen Zappala Jr. would not show the ensuing video footage of officer Kertis shooting Williams, Zappala described the events to Pittsburg Post-Gazette, which summarized them as follows: "Williams tripped over some debris, rolled and continued to move, pointing the gun at Officer Kertis and the police car. In the next 1.8 seconds, Officer Kertis told Williams twice to drop his gun... In the 2.4 seconds after that Officer Kertis fired six shots, all of which hit Williams."

Outcome: Zappala explained that, in light of the video and audio recordings and other available evidence presented, the district attorney's office concluded that Kertis acted appropriately and was justified in shooting Williams under state law. As a result, Zappala indicated that the state would not press charges against the officers for their actions. Zappala noted, however, that he had passed the case file along to the US attorney's office for an independent federal review. A spokeswoman for the US attorney's office declined to comment on the case, according to the Pittsburgh Post-Gazette.

Trampled

Background: A man saw a New York City police officer writing up a parking ticket for his Ferrari 458 Spider sports car as he was returning to his vehicle. The man nevertheless proceeded to enter the vehicle and insert his key in the ignition, after which the officer positioned his body in the path of the car.

What the video showed: Video footage of the event, shot by a citizen, shows the man activate his car's engine and begin to drive forward against the officer's direct command to remain still, rolling over the officer's foot in the process. The officer then relocated to the driver's side window and ordered the man to step out of the vehicle. After the man refused to cooperate and resisted arrest, only then did the officer use force to remove him from the car and arrest him.

Commentary: While the arrestee did not file a claim against the officer, should he have done so, the videographic evidence would have bolstered the officer's likely argument that his use of force was justified in light of the circumstances. Given that a federal appeals court has recently ruled that the public has the right to film cops in public, we're likely to see more citizen-journalists filming police interactions in the future

Good cop, bad cop

Background: After arriving at the location of a minor traffic accident involving a relative in April 2012, off-duty Los Angeles police officer Sergio Arreola begin to quarrel with, and found himself being handcuffed and booked by, a Pomona police officer named Eric Hamilton. Arreola was charged with resisting arrest and assaulting Hamilton. Arreola was then swiftly fired from his position as an officer with the Los Angeles Police Department as a result of this incident, according to The Los Angeles Times.

What Arreola argued: Arreola insisted that had not acted improperly in his interaction with the Pomona police officers and did not resist arrest. Rather, he claimed that Hamilton was the one who was hostile from the outset.

What Hamilton said: Hamilton, who was the first responder to the scene, indicated in his arrest report that Arreola refused to obey his commands, became aggressive and belligerent, and physically assaulted him. Hamilton had an audio recording device running throughout the interaction.

What the audio recording revealed: "The officer is heard telling Arreola repeatedly to 'stop resisting' and Arreola saying that he is not resisting. Arreola is also heard pleading with onlookers to record the scene. Once on the ground, Arreola said, the officers punched him repeatedly. Hamilton, he said, bent his left arm back violently and [another police officer] Tucker attempted to subdue him by using a choke hold," describes the The Times, which obtained a copy of Hamilton's recording. What's more, later in the recording, Hamilton is heard telling Arreola's wife "I'm going to make sure your husband is never a police officer in the state of California again. I'll talk to Chief Beck myself personally," referring to the LAPD chief. The recording also captured Arreola telling Hamilton, "you know I didn't do anything," to which Hamilton responded by calling Arreola "a fool," reports The Times.

Outcome: After all of the evidence, including the audio recording, was presented at trial, a jury found Arreola not guilty of the three misdemeanors to which he had been charged. The jury also awarded him $260,000 after concluding that the Pomona officers used excessive force when they unlawfully arrested him. Arreola has since been invited back to the LAPD. "It feels good," Arreola explained of returning to the police force. "I want to show the LAPD that the people who supported me and believed me were right all along," reports The Times.