What do you do if your interviewee doesn’t understand what you’re asking because they lack capacity or because you expect that they lack capacity? It is very unlikely that you, as an investigator, can make a determination about someone’s capacity. There are certainly tests the layperson can utilize to determine if someone lacks capacity because of intoxication but, beyond that, capacity determinations should not be made by investigators. If somebody lacks capacity, it often will come up. And often the person that you’re talking to will likely bring it up and say, “I have a brain injury and this makes it hard for me.” Or, “I have this learning disability and so I’m not following what you’re asking me in this regard.”
Often they’ll offer up information about altered capacity. But unless it is a thing that they have reported either to you or to the employer, you can’t draw any conclusions based on your suspicion of their lack of capacity. That being said, if an interviewee lacks capacity, get what you can from them. Did they see a thing? Did they not see a thing? They either did or they didn’t, and that’s just the investigative outcome. There’s nothing you can do as the investigator to give somebody capacity that they don’t have and so you just write about it. The analysis in the example given is not different if the person lacks mental capacity or corrective eyewear. And if that person does have documented reduction in capacity, you write about that too. Betty said she’s legally blind and she didn’t see the accident. And so we don’t think Betty saw the accident because she was credible and she lacks visual capacity. And that’s what it is.
