Having many witnesses to a crime helps the police piece together the facts. But what happens when the only witness is also the victim? Stephanie Slater was blindfolded during her kidnap but her attacker was caught because police interviewers were able to help her recall the sounds and smells she experienced during her ordeal.

But memory can be easily contaminated. Jennifer Thompson-Cannino identified an innocent man as her rapist. He spent 11 years in jail.

Now, British police use cutting-edge techniques designed to collect uncontaminated eyewitness testimony so that they can secure a safe conviction, as in the case of Louise Aird, whose home was broken into during a £2 million art theft.