Occasionally I have MPs on my site, adults, where it’s noted that they’re illiterate. I always note this information when I find it. If the person is mentally disabled (and they usually are), I note it in the “medical conditions” like this: “John Doe is mentally disabled; he is illiterate and has the capabilities of a ten-year-old” or suchlike.
Sometimes — as in a case I’m writing up now — it’s just noted that the person is illiterate and doesn’t say why. Usually, even if it isn’t said, the person is mentally disabled. (I’m pretty sure that’s the case here. It’s noted that he “may be in need of medical attention” and takes medication, and more tellingly, although this guy is in his 50s, his NamUs page says the “youth and family crimes unit” should be contacted about his case.) But you can’t assume that. Perhaps — especially with elderly people who were born in like the 1920s — they never went to school. Perhaps they have normal intelligence but a severe learning disability such as dyslexia.
In cases where the MP is said to be illiterate but there’s nothing about a mental disability or any medical thing that would cause their illiteracy, I put it in the “details of disappearance.” I wonder if “distinguishing characteristics” might be more appropriate though. Thoughts?