Handicam footage can bring criminals to justice. Beyond showing human rights abuses to the world, it provides valuable evidence in courts of law.

The Argentine Forensic Anthropology Team (EAAF) is a group of forensic anthropologists that uses video as part of its toolkit to document mass graves all around the world. They began at home, in Argentina, where over 30,000 activists were 'disappeared' during the seventies. Luis Fondebrider of the EAAF explains the purpose of their videos: The whole State is implicated in the killings, it's very complex crimes. So we need to develop a new approach using social anthropology, history, to interview a lot of relatives, witnesses, to investigate police and judicial files. Because we are expert witnesses, we have to prove what we are doing. Pictures are very important for the judge to show. Maybe you read an expert report it may be very dull because you don't understand technical terms. But a picture will show a body inside a grave, with associated bullets, it is very important.

From international investigations to local communities, video evidence can influence the outcome of trials.

An unlikely group of Welsh activists were forgotten and ignored until they made their own video letter of protest complaining of noise and pollution at a neighbouring factory in their tiny community of Pentre Maelor. Years of writing letters and petitions brought them no results, so the pensioners called upon radical, direct action media group Undercurrents for help. Undercurrents helped them make a video that included handicam footage of smoke emissions coming through the roof of the factory. When the factory owner saw the video letter, he was forced to put changes into place. And the pensioner's campaign landed the factory in court. Deeside Aluminum was fined 20,000 pounds.

Del Drury, the Pentre Maelor resident who used his handicam to record factory emissions, is convinced his footage made the difference in their fight against Deeside Aluminum. We did our little bit, with the camera, to fight against it. We won a lot of battles.

Using video isn't always this straightforward, and the trial of the officers in the Rodney King case shows that seeing isn't always believing. The now-famous amateur video shown during the trial was a dramatic example of how video images could be interpreted in radically different ways by opposing sides.

The videotape doesn't necessarily speak for itself. When people first saw 'the video', they reacted very powerfully to it. But the defense was able to use the video, at least in the first case, themselves. And they slowed it down and broke it down into discrete segments and used it as a platform from which to argue that the conduct of the officers had in fact been appropriate and consistent with their training. So the video was, in that sense, kind of a neutral tool, explains Alan Tieger, attorney for the prosecution during the second trial of the officers.

This issue has also come up at the International Criminal Tribunal for the former Yugoslavia (ICTY), where the meaning of amateur video images has been hotly contested.

Amateur video provides important evidence at the ICTY, where Slobodan Milosevic and other key military and political leaders are being prosecuted for war crimes. In practically every hearing, video has been essential in providing visual evidence of crimes committed throughout the Balkans, including the massacre of 7000 Muslim men and boys at Srebrenica.

A tape of the activities of Serbian General Ratko Mladic and his crew arrived under mysterious circumstances at the studio of British filmmaker Leslie Woodhead. When he handed the tapes over to the ICTY, it became a crucial piece of evidence against one of Mladic's generals, Radislav Krstic, who was denying that he was present at the scene of the crimes. The videotapes proved that Krstic was lying, and he was convicted of genocide and crimes against humanity. He was sentenced to 46 years in prison.

Woodhead incorporated amateur footage extensively in 'Cry from the Grave', his documentary about the Srebrenica massacre. We became aware more and more that this appalling event, the worst massacre in Europe since World War II, was what we called it in the narration "a massacre witnessed by camcorder."

Alan Tieger, senior prosecutor at the ICTY, and former prosecutor in the Rodney King case, knows the value of amateur footage for prosecuting criminals. Video technology can put in the hands of hundreds of thousands of people one of the most powerful fact-finding tools in the arsenal of law enforcement.

Milosevic and his supporters contest the legitimacy of the video evidence used against him and other Serb leaders.

Nico Varkevisser, a vice-chairman of the International Committee to Defend Slobodan Milosevic, accuses the prosecution of using staged footage in their case against the former Serb leader: The fact that images play such a role is because the prosecution's accusation was based on images... real or created images. Milosevic brings his own video evidence to the trial.