To demonstrate mens area in robbery and robbery with violence, lets first understand the meaning of the two.
Robbery involves threatening or using force before or at the time of theft in order to steal. On the other hand, robbery with violence involves stealing and the same time causing harm or death.
Robbery and Robbery with violence have no mens area because the intention here was to use force to steal. Mens area will only be applicable if the jury rules that there was no force used and therefore it is not Robbery but theft.
In theft, mens area is applicable if you argue that the person stealing thought he had the right to do so on behalf of himself or for a third person or the person whose property was stolen could not be accessed or reached. In such case, you will have to look at whether the intention was clear or not.