The legal system works on a principal of innocent until proven guilty by the evidence presented in court, but Cognitive Daily covers several studies that shown our memory of the evidence is affected by moral judgements of the person in question.
With their trademark clarity, CogDaily discuss a study [pdf] by psychologist David Pizarro that found if participants were told about man leaving a restaurant without paying, they remembered the unpaid bill being more expensive if they were told he treated the waiters rudely, than if they were told he was generally a responsible person.
It was simple but elegantly designed. Groups of people were shown clips of cars crashing and then asked how fast the cars were travelling, but with different verbs in the question.
For example, some people were asked how fast the cars were travelling when they “smashed” into each other, others how fast when they “bumped” into each other, others how fast when they “contacted” with each other, and so on.
Loftus found that simply asking the questions with a different verb altered people’s memories of the speed of the crash – like so:
“smashed” : 40.8 miles per hour
“collided” : 39.3 miles per hour
“bumped”: 38.1 miles per hour
“hit” : 34 miles per hour
“contacted” : 31.8 miles per hour
Needless to say, these sorts of tricks have been used by lawyers ever since.