Forensic Psychotherapy is the application of psychological knowledge to the treatment of mentally disordered or mentally ill patients who commit violent or destructive acts against others or themselves. Commonly applied diagnoses would include personality disorder and psychosis. The link between personality disorder and offending is not firmly established although many of those who commit offences have one or more personality disorders. The term forensic psychotherapy is usually associated with Psychodynamic psychotherapy including group psychotherapy and the therapeutic community approach. Cognitive behavioral therapy is more commonly associated with the field of psychology, particularly Forensic Psychology.
It has been difficult to illustrate a clear link between psychological interventions that successfully reduce the incidence of offending and those that do not and clearly nothing has led to the elimination of crime. At times this has contributed to a profound pessimism about the effectiveness of any treatment. This was particularly so in the United States of America but the influence spread to the United Kingdom  and arguably adversely affected the provision of rehabilitative treatments. The development of cognitive behavioural therapy which made it possible to demonstrate an effect upon some attitudes and offending behaviours and for this to be measured in controlled research studies led to the introduction of structured treatment programmes in prisons across Canada, the United States, the United Kingdom and more recently, mainland Europe. For a period there have been positive benefits in the provision of resources particularly in prison settings. However there has been serious conflict as professionals compete for limited resources and one model claimed superiority over another.
It has remained difficult to establish with great certainty which methods, if any, are effective over a significant period of time. However psychodynamic forensic psychotherapy has been shown to have some effect  as have Therapeutic Communities 
Dangerous and Severe Personality Disorder
In an attempt to establish whether it could be effective to treat serious and high risk offenders the United Kingdom Government launched a programme in 1999. This established treatment centres in two high security prisons and two high security hospitals and a further four medium secure hospitals.
Working from the premise that the offender has a complex internal world which may be characterised by punitive and unreliable internal representations of paternal and other figures, psychotherapy can shed light on the unconscious impulses, conflicts, and primitive defense mechanisms, involved in his or her destructive actions and "acting out".
The intimacy and profound experience of therapy may enable an offender to reframe and restructure these harsh imagos which tend to blunt sensitivities and, when projected out onto others, act as a rationale or driving force for criminal acting out. The patient may develop self-awareness, and an awareness of the nature of their deeds, and ultimately be able to live a more adjusted life. The effectiveness of psychodynamic psychotherapy, as is the case with other psychological therapies, is limited far as behavioral change for antisocial personality or psychopathic offenders. These two types of offenders comprise the primary diagnostic group found in forensic psychotherapy work. The evidence which is emerging, suggests that a range and variety of treatments may be most helpful for such offenders.
Treatment of high risk offenders poses particular problems of perverse transference and counter transference which can undermine and confound effective treatment so it would be usual to expect such treatment to be conducted by experienced practitioners who are well supported and supervised. References
- Martinson R. 1974, What Works?- Questions and Answers About Prison Reform. The Public Interest. 35. p 22-54
- Maguire J.What Works: Reducing Offending. Wiley. Chichester. 1999
- Leichsenring F, Leibing E. The effectiveness of psychodynamic therapy and cognitive behavior therapy in the treatment of personality disorders: a meta-analysis. Am J Psychiatry 2003;160: 1223-32
- Taylor R. A seven year reconviction study of HMP Grendon. Home Office Research Unit, London 2000.
- International Association for Forensic Psychotherapy