McCarthy is a sociologist specialising in areas of imprisonment, desistance from crime, and issues of punishment and public opinion. He has published across these areas, as well as the author of three books (Soft Policing, 2014, Palgrave), The effects of youth imprisonment on the lives of parents (with Adams, M, Routledge, 2023) and Beyond Porridge (with Adams et al, Waterside Press, 2024).