A smartphone app which records material suitable for use in criminal proceedings has been downloaded in more than 130 countries, David W Rivkin, president of the International Bar Association, told the conference.

The eyeWitness to Atrocities app 'provides the user with the ability to film or photograph atrocities and breaches of human rights when they happen, in the knowledge that the app will embed metadata to verify where and when the images were taken,' he said. 

The idea for the app came in 2010 when broadcaster Channel 4 contacted the IBA to verify what it believed was video evidence of war crimes committed at the end of Sri Lanka's civil war.

Mark Ellis, executive director, agreed that the video depicted war crimes – but said question marks over its authentication could pose challenges for its use in bringing the perpetrators to justice. He found the same went for many other videos of atrocities. 

To develop eyeWitness, the project team began with the key facts a court would need to accept a video or photo as substantial evidence assuming that the individual who shot the footage would not be available to testify.

These were encoded as a set of markets embedded as metadata recording the data and location - by GPS and Wi-Fi connections - as well as whether the file had been edited or tampered with.

A file can then be sent over the internet or physically via SD card to a secure repository hosted by legal publisher LexisNexis.

There, one copy of the material remains encrypted, while another is decrypted and analysed by legal experts. If anything is received that might constitute evidence of a human rights atrocity - namely, war crimes, genocide, crimes against humanity or torture - it is sent to the relevant jurisdiction for further investigation.

Uploaded videos are stored in a 'virtual evidence locker' with a clear chain of custody. 'We don't even need to know who is taking the video,' Ellis said. 

To safeguard users, the app separates eyeWitness material from a phone's regular photo gallery so that the images cannot be seen if the phone is seized. The app can also be fully deleted. 

EyeWitness was released by the IBA in June after a $1m investment. 'I look forward to the first conviction of a war criminal based on eyeWitness evidence,' Rivkin said.