Following a background in social science, he has since come to work mainly in the field of forensic mental health, conducting both epidemiological and health services research into the efficacy of treatments for offenders. He is also an Honorary Senior Research Fellow at East London NHS Foundation Trust and a Fellow of the Alan Turing Institute. He has also consulted on forensic mental health issues for NHS England.

Dr Freestone’s current work includes: the epidemiology of violence; outcomes research in forensic mental health services; causal inference networks for violence risk management; clinical sub-types of personality disorder and psychopathy; substance misuse as a risk factor for violence; and patterns of service use by young men in the UK. His current research is into the understanding of causal mechanisms in risk assessment using advanced statistical modelling, and the effectiveness of psychosocial interventions for offenders with personality disorder.

Dr Freestone has previously held grants from both the NIHR and ESRC. In 2015 he received funding from the UK Ministry of Justice to conduct a mixed-method evaluation of the combined Ministry of Justice/NHS England initiative to develop Psychologically Informed Planned Environments (PIPEs) within HM Prison Service and the Probation service across England and Wales.