When witnessing a situation of an victim and 'incriminator', the degree of responsibility the witness has in helping the victim or stopping the 'crime' in progress. The degree of responsibility usually depends on three criteria; 1. Whether the victim is deserving of help, 2. The competence of the bystander, 3. The relationship between the bystander and the 'victim'. The bystander can intervene in usually two different ways; direct intervention, or, calling authorities.
I saw an old lady getting her purse taken by some thug, i just stood by and watched... later i felt confused and guilty. The feeling i felt could be described as the bystander effect
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.