Pick a crime, any crime. Murder? Extortion? Littering? Grand Theft Auto.
Think about all the steps that go into that crime. Murder includes the planning (or lack of planning), disposing of the body, covering up, maybe running away. It could also include getting caught, jail, the trial, sentencing, serving time and even being released.
Focus on one step of your crime.
Write about that step. It doesn't need to be literal. You could write a step by step poem about the emotional structure of the crime. Or it could deal with the idea of what you do while you're waiting to be caught. Try to justify or at least empathize with a person who would commit this crime. They may know they're doing something wrong but feel they have no other choice. Maybe they feel entirely justified in what they've done. Look at it from more than one angle.