I have also just watched the programme. Two things strike me having read whats shown here:
1. The footage from the motorway shows two women running into the road, it does not show why. Therefore there may be a sound mental reason for that e.g. attempting to escape from the law, or they may be at that point in time unstable. The crying to each other about taking organs could be either way as two women running down the road could be trying to escape from someone.
2. The police surgeon was probably asked if the lady is fit to be questioned and or charged. This is a specific assessment they are being asked to make and relates to the state of the person in front of them at that point in time. I would hope that that assessment is informed of the recent events and medical treatment received, such as the sedation administered. The footage from the road is not directly relevant to this assessment as it is not the now, however if informed of the sedation I would hope that the mental state prior to its administration would be considered.
Zoidburg, I recognise that as a local to this incident you are concerned as to how it can have happened and could it happen again. If the people making the assessment under the MHA were unaware of the sedation then I would agree that there was a communication failure, that is not made clear in the documentry but I am sure has been part of an internal review. However we laymen looking back in hindsight can assess her mental state with the additional knowledge of the stabbing and the bridge jump. This is information which the Police surgeon did not have and colours our view. Therefore any opinion here about whether or not to section her is made on a different basis to the decision at the time and is unfair. Additionally I believe all here are commenting as laymen, yes some have firsthand medical and nursing experience of the mental health system, others have been treated by that system and some live with those who work in that system and do this job which may provide a greater level of technical knowledge. None of us though can be in the position of those individuals who were there then to remake the decision.
Additionally because these assessments are on the basis of does this person pose a risk to themselves or others as I see them before me now, then judging by the footage of her when she was released from hospital and then booked into custody I am not surprised that they may have put the earlier behavior down to substances rather than mental illness which the officer on the motorway obviously suspected.
Overall the system can be considered to have failed because she went on to kill someone. However if this is because the system was not implimented correctly or due to the limits of what society believes is a reasonable restriction to place on the mentally unwell I do not feel sufficiently qualified or informed to judge on the basis of that documentry alone. As I don't feel able to judge the cause of the failure I do not wish to assign blame to any part of that system, particularly the doctors. I consider this to an air accident board of the RAF not blaming the pilots without clear evidence they were at fault.