Researchers said many factors affected judgements of dishonesty
Researchers investigating perceptions of dishonesty have started an online "Honesty Lab", where people can view clips and decide if actions are honest.
Results of the study will be unveiled at the British Science Festival which takes place in Surrey this autumn.
In law, a person is said to have been dishonest if they were aware their conduct was dishonest in the eyes of reasonable and honest people.
But just a person's appearance could affect judgement, the researchers said.
Criminal lawyer Dr Stefan Fafinski said: "There were around two million recorded crimes involving dishonesty in 2008.
'Lying on CV'
"So the findings from the Honesty Lab in evaluating the fairness of the current test in criminal law will be of major public importance and could alter the way judicial trials are conducted."
The Honesty Lab, run by the The British Science Association and London's Brunel University, asks respondents first to look at a picture and biography of the "defendant".
Respondents state if the person looks honest, and whether the person is similar to themselves, before viewing clips of different actions and judging whether they are honest or not.
Clips being shown include actions such as lying on a CV, or knowingly purchasing a pirate DVD.
They also include using office stationery for personal use.
Researchers have predicted there is no common standard of dishonesty in today's society because there are many factors that affect judgement - such as how the defendant looks, and whether the people judging can relate to the person or the act in question.
They are aiming to get 20,000 people to complete the online study over the summer.
The British Science Festival is being held in Guildford from 5 to 10 September.