The role of daily living skills in forensic psychiatric patients in relation to psychotherapeutic progress and the potential reduction of dangerous behaviour has been neglected in the scientific discussion about clinical instruments for the evaluation of dangerousness and recidivism. This is mainly due to the lack of adequate observationally based instruments allowing for valid and reliable therapeutic assessments. Therefore, a new means of assessment focusing on daily living skills and social risk (the BEST-Index [Behavioural Status Index] was applied to n = 86 German forensic psychiatric patients. Two widely known actuarial instruments tapping violence risk were administered for cross validation (Psychopathy Checklist Revised [PCL-R], HCR-20). Within intervals of nine months, all instruments were applied three times. Sufficient inter rater reliability and good convergent validity of the sub-scales in relation to the actuarial instruments (HCR-20, PCL-R) could be demonstrated; supported by empirical data, clinicians working with the BEST-Index may use it to monitor behavioural change over long treatment periods. It is suggested that treatment planning and evaluation of mentally ill offenders might profit from its use.