"Duty of care"

is a term used to describe the responsibility one person has towards other people. It is often used in professional relationships.
It came up recently when Middle Cat was seeing our GP. Middle Cat had major back surgery two years ago but still experiences severe pain. She has very strong painkillers of the type that can only be prescribed by a doctor. Both of them are well aware of the dangers of using these long term. Our GP has a duty of care to inform Middle  Cat and to try and keep the amount to a minimum. 
Middle Cat knows these things. She trained as a physiotherapist. She has a son who is a doctor. 
I also know something about these things. Over the years I have picked up a good deal of medical knowledge simply through working with so many doctors and finding ways to inform other people about the things they need to say and do.
But there was a piece in the paper this morning about the grief a father felt for the loss of his wife and child in a murder-suicide. His feeling, possibly completely correct, was that it was brought on  by his wife's inability to cope with her then present pain and the strong possibility that in a couple of years she would be in a wheelchair. Multiple sclerosis? Perhaps. I don't know. It doesn't matter what the diagnosis was now. It's too late. She felt she  couldn't cope.
I wonder though how the last doctor she saw feels? I doubt he or she is anything but distressed at losing a patient like that. They must be wondering, "what did I miss?" and "what else could I have done?" They will almost certainly feel they have failed in their duty of care towards their patient. But how often does it happen?
I know someone, an older person, who recently changed GPs and was shocked to discover that her previous GP had not picked up several serious issues. Perhaps s/he was too familiar with the patient and simply missed the signs?
I know I try to avoid going to see any member of the medical profession but I hope I am not stupid about it. I do go to get essential doctor-prescribed medication. If I felt ill or suspected something was seriously wrong and not likely to right itself in a short space of time and without help I would go. But I won't go for the common cold or, potentially, a number of other ailments that  I know I am likely to recover from without help. I don't want antibiotics if I can possibly avoid taking them. They aren't going to help me recover from the 'flu - for which I have had a short anyway.
I am wondering whether doctors are missing things because they are overworked and whether that "duty of care" has been replaced, to some extent, by form-filling. Is that why the country GP missed the danger signs and a woman killed her child and then herself?
And it is perhaps why the Whirlwind's father left me an email this morning and said, "Care to say something on your blog Cat?"
He knows and the Whirlwind knows that there are some questions which will never be answered.