A thesis, sometimes also known as a dissertation, is a written piece of work that supports a student's study in the quest for a first degree or higher. A degree takes three years to study full time, and throughout that period, the student is always aware that a thesis could be one method of appraising his or her learning. Because of this, there is a lot of focus on it.
• Subjects studied
Any subject will encompass many things and so there is always a level of autonomy for a student to select aspects of the subject that they are learning. For example, someone choosing to study English Literature would find it impossible to study at the level required all aspects of this choice and so will opt to choose certain aspects of it.
Criminology Research is also a massive subject, and so you will have specialized in some areas more than in others. A thesis always takes hard work and serious study to complete, and so you should focus your attention on some aspect of your studies that you have particularly enjoyed, or that you feel that you will get more out of when you have studied it in more depth.
Once you start to put some ideas together and realize what direction you are going in, you will be in a better position to think of a title for your thesis.