Roles of a forensic nurse vary according to the country in which you reside. In the United States this can be "death investigator, nurse coroner, clinical nurse specialist, sexual assualt nurse examiner, forensic psychiatric nurse, correctional nurse, legal consultant nurse, nurse attorney, forensic nurse educator/consultant, forensic paediatric nurse and forensic gerontology nurse" (Evans.A.; & Wells, 2001, p 38.).
In the New Zealand Health System it is care provided specific to the mentally ill offender.
It focusses on risk assessment and management, knowledge and application of the law and knowledge of the application of principles relating to recovery from mental illness and violence.
In NZ we have court liason nurses, community psychiatric forensic nurses, and inpatient forensic nurses.
As you can see USA has a larger scope and focusses on the "victim" we focus on the offender.
Evans, A.M. & Wells, D. (2001). Scope of practice in forensic nursing. Journal of Psychosocial nursing and Mental Health. 39 (1).