Not certain, but this is probably the U.S. study Derman has referenced: It is by the U.S. Department of Justice and the Bureau of Justice Statistics. This description is directly from the report:
The findings in this report are based on the Bureau of Justice Statistics (BJS) National Crime Victimization Survey (NCVS), a household survey that collects data on U.S. residents age 12 or older (excluding those living in institutions). The NCVS adopted survey questions from the U.S. Census Bureaus American Community Survey (ACS) to identify respondents with disabilities. The NCVS defines disability as the product of interactions among individuals bodies; their physical, emotional, and mental health; and the physical and social environment in which they live, work, or play. Disability exists where this interaction results in limitations of activities and restrictions to full participation at school, at work, at home, or in the community. Disabilities are classified according to six limitations: hearing, vision, cognitive, ambulatory, self-care, and independent living.
The report defines Ambulatory Limitation as "difficulty walking or climbing stairs." The National Crime Victimization Survey (NCVS) "collects information on nonfatal personal crimes (rape or sexual assault, robbery, aggravated and simple assault, and personal larceny) and household property crimes (burglary, motor vehicle theft, and other theft) both reported and not reported to police."
So, according to the basis of this report (highlighted above in blue) you can see that Derman perhaps exhibited a bit of bias when Nel asked if one should take into consideration the supportive environment and individual circumstances of OP's disability, and he said he strongly disagreed. Hmmm... not good, Professor.