Swedish penal law does not exculpate on the grounds of diminished accountability; persons judged to suffer from severe mental disorder are sentenced to forensic psychiatric care instead of prison. Re-introduction of accountability as a condition for legal responsibility has been advocated, not least by forensic psychiatric professionals. To investigate how professionals in forensic psychiatry would assess degree of accountability based on psychiatric diagnoses and case vignettes, 30 psychiatrists, 30 psychologists, 45 nurses, and 45 ward attendants from five forensic psychiatric clinics were interviewed. They were asked (i) to judge to which degree (on a dimensional scale from 1 to 5) each of 12 psychiatric diagnoses might affect accountability, (ii) to assess accountability from five case vignettes, and (iii) to list further factors they regarded as relevant for their assessment of accountability. All informants accepted to provide a dimensional assessment of accountability on this basis and consistently found most types of mental disorders to reduce accountability, especially psychotic disorders and dementia. Other factors thought to be relevant were substance abuse, social network, personality traits, social stress, and level of education.