Purdy, Pretty, Campbell … and the case of a Paisley snail

The detail of their lives and character were argued over by men and women in wigs and gowns, and dissected in open court, but when the judges ruled, the legal juggernaut rolled on. The individuals usually returned to obscurity but their names live on as shorthand in the adversarial exchanges between lawyers in new disputes decades, or even centuries, on.

It is doubtful if Cases That Changed Our Lives will ever replace the weightier legal textbooks, but it has a value for those with a passing interest in the law as a reminder that behind every footnote there were living, breathing humans.

A few whose cases are explored in this collection deliberately sought their 15 minutes of legal fame. They had a point to make and somehow found the means to make it. Naomi Campbell took on Mirror Group Newspapers to assert, largely unsuccessfully, her right to privacy.

In far off 1986 Victoria Gillick, mother of ten children – including five daughters – decided to challenge the lawfulness of medical practitioners giving contraception to a girl under the age of 16 without the knowledge of her parents. She lost the argument in the House of Lords, though the authors of this essay, Janet Bazley QC and Stephen Jarmain, argue the legacy of the case has been to move the perspective of the courts away from a parent's rights to control a child to their responsibilities towards the child.

Similarly, Debbie Purdy and Diane Pretty initiated cases that sought clarification of the criminal law on assisted suicide.

Diane Pretty suffered from the degenerative condition motor neurone disease. She had sought an undertaking from the Department of Public Prosecutions in England that if her husband assisted her in fulfilling her wish to end her life he would not be liable to charge under the 1961 Suicide Act.

Successive judgments went against her, all the way to and including the European Court of Human Rights which ruled the articles enshrining an individual's right to life could not be read in reverse to allow an individual to choose to die. The author Lynne Townley records that Diane Pretty died – within two weeks of the judgment – in the way she had feared most, choking and struggling for breath before falling into a coma for several days.

Debbie Purdy picked up the legal baton to secure a significant change in emphasis from the House of Lords in 2009, with five Law Lords delivering the leading judgment ruling that Article 8 of the European Convention of Human Rights, the right to respect for private life, applied.

The consequence was that the Crown Prosecution Service published in February this year its 'Policy for Prosecutors' which sets out the factors that would influence its decision on whether to prosecute someone who had assisted in a suicide.

The Crown Office in Scotland has notably failed to follow the lead, taking refuge behind the fact there is no equivalent of the Suicide Act in Scotland.

Rather more of the roll call of the footnote foot-soldiers in the collection is made up of individuals or enterprises which had no expectation or desire for fame or notoriety, and certainly never decided they actually wanted to see the inside of the House of Lords or Supreme Court or European Court of Justice. They were probably barely recognised outside their own home, though their name is on the lips of the most learned men and women of the land.

The signs are that the presumptions on which thousands of police investigations every year in Scotland are based are likely to be overturned on the 26th of this month when the Supreme Court of the United Kingdom delivers its judgment in the case of Peter Cadder.

His status as a footnote is assured, although the facts of the initial incident which led to him being charged with assault and breach of the peace are indistinguishable from thousands of others every year.

"That's part of the excitement of doing appeals," says advocate Claire Mitchell. "You get a file in your box and when you first open it you have no idea whether it will be a Cadder and catch the attention of the judge or whether it will arrive from obscurity and disappear back the same way, with the judge wondering what on earth you were on about."

It wouldn't be too unkind to suggest that the central figure in the only Scottish case in the collection, May Donoghue of Donoghue v Stevenson, was in most senses unremarkable, although the case that bears her name is recognised internationally as the foundation stone of modern consumer-protection law. Preparations are already under way for a two-day conference in Paisley in 2012 to mark the 80th anniversary of the House of Lords judgment in the case.

The basic facts are reasonably well known, that in August 1928 May and an unnamed friend went to the Wellmeadow Caf in Paisley. The friend bought May a bottle of ginger beer. Some was poured over an ice-cream float which May started to eat, while the remainder in the bottle was taken to the table. When the bottle was emptied into May's glass, along with the ginger beer slid the decomposing remains of a snail.

May was later unwell and eventually was directed to Glasgow solicitor Walter Leechman who raised an action against David Stevenson, proprietor of the bottling company.

"What a star," says co-author of the essay, Paul Reed QC. "If anybody ever needs an example of a professional committed to the pursuit of principle on behalf of his client they should look to Walter Leechman.

"It is one of the finest aspects of the solicitor's profession that he knew there was an issue of principle and was determined to pursue it. Sometimes you can't understand developments of our common law unless you understand the individuals who drove them."

In fact, Walter Leechman had been on the case before but had been defeated in the Court of Session in Mullen v A G Barr and Company Ltd in the matter of a dead mouse in a bottle of ginger beer. He had the bit between his teeth when Mrs Donoghue appeared. His legal team offered its services for nothing as he argued that the manufacturer and bottler had a duty of care to the end consumer. The law as it stood recognised principally defined contractual relationships.

The argument was accepted in the Court of Session, then defeated on appeal by Mr Stevenson. Mrs Donoghue was formally declared to be a pauper in order to raise an action in the House of Lords without having to cover the costs of the other side if she lost.

In May 1932 the House of Lords ruled by 3-2 that a manufacturer did have a duty of reasonable care to the consumer. If product liability as we know it was not born in that judgment, it had life breathed into it.

• Cases That Changed Our Lives Ed Ian McDougall, LexisNexis, 12.99