The proliferation of CCTV cameras has also led to an increase in the availability of identification evidence. According to the Police Foundation, the UK now has more surveillance cameras than any other country in the world, and footage is used to solve around 160,000 criminal cases a year. When CCTV footage is used to identify someone in court, a police officer or relative may claim to recognise that person from the footage, a jury might be asked to compare the defendant to someone in CCTV images, or an expert can use facial mapping techniques to compare the defendant's face to that of the suspect.
Under the Turnbull guidelines - introduced in 1977 by a judge who found that visual identification "can bring about miscarriages of justice and has done so" - a judge has to warn the jury of the need for special caution when relying on such evidence. But eyewitness testimonies can still be one of the most persuasive types of evidence a jury will hear. "A witness standing up and saying: 'That's the man, I saw him, I will never forget his face' is extremely compelling to a jury," said Valentine. "Witnesses can be completely honest and be mistaken."
Psychological experiments have shown that facial recognition from CCTV can be as prone to error as traditional eyewitness evidence. In an experiment which looked at 600 identity parades, a fifth of eyewitnesses picked the wrong person, Valentine said ... "