The true thief was not offered as a suspect choice in the line-up. This meant the participants in the study had to rely on their own judgements and bias to choose suspects.
The results found that 51 per cent of participants accused muscular suspects of being the perpetrator in the video.
Meanwhile some 37 per cent thought suspects of a normal weight were most likely to have committed the crime. Just 10 per cent believed overweight suspects could be the aggressor.
Dr Julia Shaw, senior lecturer in criminology, who carried out the study, said: "Stereotypes about body type may be getting in the way of justice.
"Our findings suggest that if you are an innocent suspect of a crime but happen to be muscular, you may be at a significant disadvantage.
"Body type is often overlooked as a basis for discrimination, and has rarely been examined in legal contexts.
"The present research is evidence that the body type of a suspect can impact the partiality of eye-witness accounts."
The research on 93 people was published in the journal Psychiatry, Psychology and Law.
