Whether dementia related or not that is exactly what I am saying.
Obviously if both were being asked to identify someone from an incident they had seen then it would be as you suggested but for something like this there would not be a problem. If the Mother lacks capacity & depending on what she can remember I would say she wont even be made to go through a formal interview process.
I think we are at cross purposes. My post related specificially toi a case where the statement of a person with dementia was being taken as a formal part of the evidence-gathering process with a view to use in a prosecution. In such circumstances, then the presence of any other witness during that process would risk making any evidence from that statement inadmissible.
If the person with dementia was being interviewed
informally, then, as you say, there would be less of an issue, but also less point to the interview, and, frankly, I'd expect the police not to go down this route beyond establishing that the perosn concerned existed. The law on criminal evidence is pretty strict, and in such cases, as I posted earlier, I'd expect the police to rely on forensic accounting and interviews with third parties, simply because they will yield the most reliable and usable evidence. Such cases can be very difficult to prosecute, and prosecution is (normally) secondary to the stopping of the fraud/financial abuse and any potential recovery of assets.
W