In essence, the thorny issue of assisted dying boils down to the principle of ‘do no harm’.

Those in favour of a change in the law believe that terminally ill human beings are suffering needless pain because they do not have the right to request a lethal prescription to hasten their death.

Opponents insist that once courts grant permission to doctors to end dying patients’ lives prematurely it is only a matter of time before the disabled or frail elderly come under pressure to die rather than “burden” their families or care services.

READ MORE: Spanish bioethics expert says claims assisted dying threatens elderly and disabled is wrong 

A key problem in the current situation is the inequality of access to assisted dying. The practice is unavailable anywhere in the UK, but those with the funds - around £10,000 for Dignitas in Switzerland - can pay to go abroad instead.

Secondly, the physical strain of making the journey means that many patients have to travel abroad to end their lives earlier than they would wish.

But opponents point to horrors such as Nazi Germany’s ‘Euthanasia Program’, where more than 250,000 children and adults were gassed, starved to death or killed with fatal injections or drug overdoses.

It began in 1939 when parents of children with mental or physical disabilities were encouraged to admit them into paediatric clinics across Germany and Austria, and was later expanded to include adults institutionalised with disabilities, psychiatric conditions including dementia and schizophrenia, neurological disorders such as epilepsy, and those deemed “criminally insane”.

By the end of the war, the Program included individuals crippled by bombings and geriatric patients.

READ MORE: MS patient moves 200 miles for disabled-friendly flat after deferring assisted suicide 

There is a huge difference, however, between Richard Selley’s appeal to lawmakers to give patients like him with Motor Neurone Disease (MND) the right to die, and a state-sponsored conspiracy to wipeout individuals whose lives are not considered worth living without their consent.

If the laws do change - and the Scottish Parliament has the powers to do so - the likeliest avenue would be the Oregon model, first pioneered in the US state in 1997.

It entitles adults with a terminal illness and an estimated six months left to live to request that their doctor prescribe a lethal dose of medication. Unlike the physician-assisted suicide proposals rejected by MSPs in 2015, this model places the onus on physically administering the drug squarely on the patient. The implication of course is that this ensures their action is entirely voluntary.

The model has now been adopted widely in the US and Canada, and in parts of Australia.

Between 1998 and 2015, a total of 1,545 patients in Oregon - aged 25 to 102 - obtained a lethal prescription. Nearly 80 per cent of those patients had cancer.

READ MORE: Lack of right to die law in Scotland scares me 

According to a study by oncologists at Oregon Health & Science University, the number of lethal prescriptions being issued has increased steadily since the law came into effect.

Although the researchers said there is no evidence of the law being abused, they noted that around a quarter of patients said they were ending their life because pain had become unbearable.

Such suffering cannot always be eliminated, however, and campaigners believe people should have the right to choose what they endure.

Sir Graeme Catto, the Aberdeenshire-based former president of the General Medical Council, wrote the foreword to Dignity in Dying’s report earlier this week which concluded that 11 Scots a week die in agony even with access to the best palliative care.

Sir Graeme said: “Richard Selley chose to control his final days by travelling to another country to have an assisted death, rather than face a long, drawn-out death from motor neurone disease that was in store for him.

“We must ensure that Scotland is a society where nobody is forced to endure a painful, undignified, harrowing death against their wishes.”

The Oregon researchers also found that 3% of patients used the law because chemotherapy was too expensive - an injustice that the NHS model of care must protect against.

For critics, the Oregon model is a step too far. For others, it unfairly excludes those who find their lives unbearable as a result of incapacitating conditions such as MS, MND or locked-in syndrome, but whose life expectancy exceeds six months.

It will be up to MSPs to wrestle with this conundrum again - at some point - but the outcome is impossible to call.