Marion's research interests encompass the sociology of punishment, criminal law, and human rights. Her book, Normalising Punishment: the case of life without parole in America will be published by Oxford University Press in 2019. It explores the ties between life without parole (LWOP) and efforts to remove capital punishment. The book draws on a unique database of over 300 letters written by prisoners serving LWOP in California. Marion continues to be interested in topics relating to life imprisonment and the politics of punishment more broadly. Her other research inquiries include race, gender, and migration studies.
She is happy to supervise graduate and postdoctoral students working on topics that relate to prisons, punishment, and human rights.