Voter/Candidate eligibility

Just heard the news that Sanjay Dutt is not approved to stand in the elections because there are charges against him. I am not into politics at all nor I am interested in it. Also I am not a fan of Sanjay Dutt, but a thought came into my mind when I heard this.

People say that guys who have criminal cases against them should not be allowed to stand in elections. I inquired from someone that people who are in jails also vote during elections. I think that they should also not be allowed to vote for anybody because they have criminal cases against them. Also, why should people be allowed to vote who have done some kind of crime.

What do you guys think? Please comment!!