Narrowing down

The two topics that I narrowed it down too would be The Nicotine topic and the Serial killer topic. I finally decided to do my research paper on serial killers. This interests me because I always wondered what runs through the mind of serial killers? How so they become so aggressive? What was their childhood like to make them want to kill? Do these killers think that they are perfectly fine and nothing is wrong with themselves? These are all the questions that I hope to find in my research while writing my paper. I will start looking for books and articles to help me answer hopefully all of these asked questions.