The significance of malingering or symptom exaggeration and its appropriate assessment have become increasingly recognised on an international scale. In the field of neurocognitive disorders, not only medicolegal cases, but also a number of clinical conditions are considered especially pertinent for assessment. This case report deals with a 22-year old patient who had suffered a moderately severe brain injury in a car accident almost three years before. In the context of seeking financial compensation from an insurance company, he claimed complete retrograde amnesia for all events and information prior to the accident. Moreover, he presented a Ganser-like response pattern (subsequent near misses) when trying to solve mathematical problems. Therefore, forced-choice symptom validity testing was performed with simple maths tasks. His response pattern was clearly less than random, indicating controlled incorrect responses and, thus, negative response behaviour. When confronted with this interpretation, he relinquished symptom exaggeration and was able to solve these tasks appropriately. While symptom validity techniques belong to the repertory of neuropsychologists in a number of countries, this is not yet true for Germany. However, their application will increasingly be encouraged to meet quality standards of medicolegal assessment.