One of the reasons that Margo MacDonald, the Independent MSP, has relaunched her bill to give terminally ill people in Scotland the right to assisted suicide is that she believes the public has a greater awareness of the issues than when she first introduced a bill on the subject in 2010.

That is almost certainly true. High- profile cases such as that of Tony Nicklinson, who fought for the right to end his life, and famous supporters of change such as the writer Terry Pratchett, have ensured the issue has grown in the public consciousness.

The settled view of the public on the issue is much harder to discern. The campaign group Care Not Killing, which is made up of a number of faith groups and healthcare professionals, has been making clear its opposition to Ms MacDonald's plans but the polls also show support for assisted suicide has been growing.

The legal position is also unclear. In England, it is unlikely that a person who helped another to die would be prosecuted because the Director of Public Prosecutions has said so. But there is no such legal guidance in Scotland, which means that prosecution would be possible, if not probable.

Ms MacDonald's bill seeks to change this, but its implications should be considered in principle and in practice. In principle, it is hard to accept a situation in which a terminally ill person who is able to commit suicide can do so, but if they are incapacitated, this option is not open to them. This can, and does, lead to circumstances in which a person in terrible pain, along with their family and friends, has no option but to endure the suffering.

However, even if we were to accept the principle that someone in such circumstances should be allowed to take their life, there are serious practical concerns about the assisted suicide bill. Ms MacDonald is aware of these and has clearly tried to address them with provisions to ensure that any request to a GP would have to be backed up by a second professional opinion. There would also be a two-week period in which the patient could change their mind and perhaps most importantly the licensed facilitator, who would collect the necessary drugs and agree the process of assisted suicide, would have no personal relationship with the patient (which may go some way to dealing with the worry relatives might take part in the process for personal gain).

These provisions might help change the minds of some MSPs, although the bill was pretty thoroughly rejected last time and concerns persist. The most important - which was raised by The Church of Scotland in The Herald yesterday - is that the right to die may become a duty to die. In other words, some vulnerable people might feel pressured into accepted assisted suicide.

The position of doctors also remains a barrier. One retired GP, Dr Bob Scott, told this newspaper he would be willing to help patients die, but the majority of doctors remain opposed largely because they worry that the trust on which the patient-doctor relationship is based would be undermined.

Even more importantly, there is the question of the duty of doctors, and society, to the most vulnerable. That must be protected at all costs and if there is any question of the bill on assisted suicide bill threatening that, MSPs should vote against it.