About us
Criterion A is the diagnostic criterion within PTSD that refers to exposure to a traumatic event. It represents the point at which an experience has the potential to profoundly alter a person’s psychological functioning.
Criterion A Psychology provides specialist clinical psychology services for individuals, organisations and the courts. Our work includes expert witness assessments, psychological therapy, training and consultancy, with particular expertise in trauma, coercive control, memory, resilience and psychological functioning under conditions of adversity.
About Criterion A Psychology Services
Criterion A Psychology is an independent specialist clinical psychology practice founded by Dr Brock Chisholm, Consultant Clinical Psychologist. The practice provides expert witness services, psychological therapy, training and consultancy across healthcare, legal, organisational and humanitarian settings.
The practice was established from a commitment to applying clinical psychology where it can make the greatest difference—supporting individuals affected by trauma and adversity, assisting the courts through independent expert opinion, and helping organisations understand and respond to complex psychological issues. While the practice originated in trauma psychology, its work now encompasses a broader understanding of how adversity, coercion, stress and psychological vulnerability influence human functioning.
Dr Chisholm has worked with people affected by a wide range of experiences, including psychological trauma, serious violence, abuse, coercive control, torture, trafficking, humanitarian crises and other forms of adversity. His work integrates clinical practice, psychological assessment, research and expert witness evidence to provide clear, evidence-based opinions and interventions.
Criterion A Psychology provides services to individuals, legal professionals, public bodies, charities, media organisations and other institutions requiring specialist psychological expertise. Whether delivering therapy, preparing expert reports or providing professional training, the practice is committed to scientific rigour, clinical integrity and practical application.
In addition to clinical work, Dr Chisholm has acted as an Expert Adviser to the National Crime Agency, is an approved expert witness for the International Criminal Court, and has contributed to national and international initiatives relating to trauma, violence and resilience. His work increasingly focuses on understanding how people adapt, survive and recover under conditions of adversity, with this research informing all aspects of the practice.
Employment opportunities
We are always interested in experienced clinicians who would like to join our bank of staff.
Please contact us with your CV if you would be interested in working with us.