Observer wrote:
Above advice is NOT correct. It is the keeper and "any other person" who has the obligation to provide information (although the exact nature of the obligation differs. In the circumstances described, you almost certainly gave possession of the vehicle to your wife, so you should nominate her as the driver. This does NOT prove she was driving. It merely diverts the investigation trail to your wife and ensures you cannot be charged with a s.172 offence. It will then be up to your wife, if she genuinely can't recall whether it was she or her sister driving, to say so; and that may be (quite likely will be) tested in court.
Observer sorry but you are wrong to state that the advice is incorrect. As I posted above, S172 s2) b)
(2) Where the driver of a vehicle is alleged to be guilty of an offence to which this section applies—
(b) any other person shall if required as stated above give any information which it is in his power to give and may lead to identification of the driver.It is NOT the obligation of the RK to interrogate 'any other person', or relay the opinions or statements of 'any other person' it is the police. The RK has discharged his obligations by naming two 'any other persons'
Observer wrote:
As you were not in the vehicle, it is obvious you cannot identify the actual driver with certainty.
we agree on this bit but
Observer wrote:
Don't think you can shield your wife by claiming doubt in your mind. As far as you are concerned, I suggest there is no doubt that your wife was 'charged' with responsibility for your car on that day.
Thats up to the police to find evidence as to whether its the wife of wife's sister, not the RK
Observer wrote:
p.s. I assume your sister is insured to drive your car? If she is not, your wife's claim that she can't remember would look a bit suspect, or she may open up an offence or 'permitting'.
You are just trotting out the frighteners used by the SCPs here Observer

It may well be that the car is insured for any user and quite possible that the wife's sister has an "any car not the property of the insured...." clause on her own insurance. Provided the wife asked the wife's sister and she responded in the affirmative that should be quite sufficient as far as the wife is concerned.