So, just as in the United States and other places where social media has enabled protest, citizens who feel marginalized are using the videos to seek justice when law enforcement officers abuse their authority.  “There is a general sense that law officials can do pretty much whatever they want,” said Vincent Foucher, an analyst with the International Crisis Group, who has worked extensively in West Africa. “Images are a very powerful way to bring up these issues.”  In Nigeria, capturing law enforcement abuse is so popular that people send in videos and photos taken from scenes of military brutality, bribery by public officials and other misconduct to one of the nation’s biggest television stations, which shows them in a segment called “Eye Reports” during its main news program.  “They are now part of the reporting of the good, the bad and the ugly of the country’s social life,” says Lanre Arogundade, the coordinator of the International Press Center in Lagos, Nigeria’s commercial capital.  Human rights workers say that the practice of sharing videos in West Africa is a natural extension of longstanding frustrations with abuse of power in the region. But even with today’s ability to capture and broadcast evidence immediately, the videos have not always produced tangible results. Often the clips are hard to verify, and few prosecutions have followed, experts say. Scenes of police officers seeking checkpoint bribes or beating civilians sometimes amount to no more than a handful of Facebook comments expressing indignation.  But little by little, many of the videos shared on social media are chipping away at impunity and in some cases drawing widespread attention to problems that the authorities are finding hard to ignore.  “These have led to, if not prosecutions, at least more awareness and discussion of violations, and that is really important,” said Sabrina Mahtani, West Africa researcher for Amnesty International.  In areas where law and order is scant, videos are sometimes shared online by supporters of the police — as a cautionary tale of what happens to wrongdoers who are rightly, if violently, punished for doing bad things. But once they make their way across social media, they are sometimes cited as evidence of abuse by security forces, evoking outrage and injustice.  In the video of the officer shooting the man in Ivory Coast, for instance, one onlooker can be heard saying, “Again, do it again!” after the officer shoots the man the first time. Others in the crowd appear to egg on the officer, and at the end of the clip, another person off camera can be heard saying, “Don’t film him, don’t film him,” adding, “You are going to get that police officer in trouble.”  But as the video made its way across the internet, it prompted an uproar in Abidjan, the nation’s economic capital, where the officer was arrested and an official investigation was opened. In a statement widely reported by the local news media, the chief of the Ivorian national police force said it “will not tolerate behavior from its officers that is contrary to the ethics of human rights.”  In July, Sheriff Shittu, who is not a law enforcement officer, was stuck on a highway in Lagos watching a scene he felt deserved the collective outrage of the internet.  A soldier was beating a bus conductor, waving a gun and threatening to shoot the man. Other soldiers joined in, shouting, “We’re going to kill him.”  “That was when I took out my phone and started recording,” said Mr. Shittu, who posted the video on YouTube. “It’s a deterrent to abuse and power. This guy didn’t do anything wrong.”  Mr. Shittu said he was inspired by the success of American videos in drawing attention to violence by law enforcement officers and had seen videos of similar episodes shared online that resulted in soldiers being disciplined in Nigeria.  “In the past nothing would happen,” he said. “That’s changing now.”  In Conakry, Guinea, a video that was circulated on the internet several months ago showed an armed robbery suspect with his hands and feet tied to an iron bar. Uniformed national police officers paraded him around, suspending him from the bar like an animal carcass, in an attempt to get a confession. “You’re breaking my hands!” the suspect shouts.  One of the officers at the scene that day posted the video on his Facebook page, apparently for bragging rights. But it was shared across social media, prompting denunciations from Guinean human rights organizations.  The Guinean government, which passed measures in 2011 aimed at cracking down on forced confessions, suspended 13 officers over the episode and opened an investigation into using torture to extract confessions.  Cellphone-armed citizens certainly have not put a halt to abuses of authority. In Nigeria, the military has been accused of killing countless civilians in recent years. And in some nations, government opposition forces and protesters have been threatened, beaten, jailed or sometimes killed without consequence, even when the abuse was captured on video.  But police abuse is not the only issue the videos help address. This spring in Cameroon, onlookers captured a horrific scene outside a hospital, leading to a national outcry about the state of the health care system.  Monique Koumate, who was pregnant with twins, arrived at a hospital in distress and died before she entered. En route to the morgue, her relatives noticed that the fetuses, apparently still alive, were moving inside Ms. Koumate’s body. They rushed back to the hospital but were unable to summon help. Desperate to save the babies, one relative placed Ms. Koumate’s corpse on the sidewalk and sliced open her stomach, pulling out the babies and resting them on her stomach.  It was too late. They were dead.  The gruesome scene went viral online. A Twitter hashtag #MoniqueKoumate was created, and accusations were aired that the hospital had turned away Ms. Koumate because she could not pay for care.  The public outrage prompted the hospital to investigate and led to a report by the National Order of Doctors of Cameroon citing deficiencies and calling for better maternal health care.  But police abuse is still the focus of many people, with numerous Facebook and WhatsApp groups in the region dedicated to sharing videos on the topic.  In Freetown, the capital of Sierra Leone, passers-by were already recording when Yasmine Bilkis Ibrahim pulled out her phone to film an officer screaming and waving his gun at a terrified unarmed man after an apparent traffic altercation.  “I will kill you,” the officer yelled at the man. “And nothing will come of it.”  Ms. Ibrahim, 24, made an immediate link to what is happening in the United States. “If people can use such videos in America to demand justice, I believe we can also demand justice using the same method,” she said.  Brima Kamara, a spokesman for the Sierra Leone police, said he belongs to a WhatsApp group, called “Talk With the Police,” made up of police officers, politicians and regular citizens.  People often submit video clips to the group, alleging police misbehavior. One recent submission showed two officers fighting. The men were suspended and sent back to the police academy for more training, Mr. Kamara said.  He said the videos help improve the police force in a nation still recovering from a brutal civil war that ended 14 years ago.  “We often advise officers to be careful of their actions in public because at this age they can’t get away with crimes or actions,” Mr. Kamara said. “Now with the involvement of social media and the smartphones, everything goes public in just a minute.”  Sean Lyngaas contributed reporting from Abidjan, Ivory Coast; and Tony Iyare from Lagos, Nigeria.  A version of this article appears in print on September 17, 2016, on page A1 of the New York edition with the headline: Africans Turn a Video Lens on the Police. Order Reprints| Today's Paper|Subscribe
Citizens are increasingly deploying social media in nations where corruption and abuse by security forces sometimes occur with few repercussions.