‘NOBODY goes to the electorate on the platform of “your secrets are not safe with me”.’

In court number one in Parliament House yesterday, Jonathan Mitchell QC laid out the case against Alistair Carmichael. During the 2015 General Election campaign, the Secretary of State took to the airwaves to deny any involvement in leaking an ambassadorial memo to The Telegraph, which suggested that Nicola Sturgeon wanted David Cameron to be reinstalled in Downing Street.

Carmichael denied all knowledge of how this confidential document found its way into the public domain. “The first I became aware of this,” he told Channel 4 News, “was when I received a phone call from a journalist making me aware of it.”

As the Orkney and Shetland MP subsequently admitted, this was a whopper: a brazen falsehood. Carmichael knew perfectly well how The Telegraph had acquired the memo. He’d green-lit – instructed – his special adviser to disseminate it. But on

May 7, the electorate of Orkney and Shetland was denied this knowledge. Some – many – may have taken Carmichael’s denial at face value.

They were deceived. The four petitioners argue this falsehood engages section 106 of the Representation of the People Act. Carmichael, they suggest, lied about his “personal conduct and character” to secure re-election in Orkney and Shetland. This case isn’t about the leak: it is about the cover-up. On Monday, Roddy Dunlop QC, for Carmichael, argued that this was all politics. Carmichael’s leak was political. His subsequent deception and denial were political. It isn’t the job of the courts to regulate the rough and tumble of democratic politics, he suggested. And if the court accepts Dunlop’s argument – that Carmichael’s was a political, not a personal, lie – his election stands.

Yesterday, Mitchell hit back. “Whether or not the leak is political, nothing in politics called on him to lie about this,” he said. It isn’t a question of politics, but of Carmichael’s “honour, veracity and purity”. It was, in short, eminently personal and caught by the 1983 Act. The Liberal Democrat MP had put “onto the scales his reputation of personal trustworthiness”. The election court, Mitchell argued, was entitled to hold him to account for it.

On Monday, Dunlop suggested that if the petitioners prevailed, politicians would be “strapped to a lie detector and administered truth serum” during elections. The Orkney four’s case is more modest: those in public life shouldn’t tell lies, encourage voters to believe their lies, and benefit from that dishonesty. The hurdles to bringing election petitions are formidable, the cost astronomical, the timetable tight. Courts should not intervene in elections too readily. But if all of Carmichael’s sins are political – what does this say about public life in this country? If the courts grant politicians impunity to lie to their electorates, what have candidates to fear?

Some suggest this case is a partisan witch-hunt, a transparently empty and vexatious legal suit, pettily pursued. It is not. Mitchell’s case relies on a novel construction of a tricky point of law, inviting a court to do something courts aren’t terribly comfortable doing: embroiling themselves in politics.

The petitioners have an arguable case. In fighting it at considerable personal cost, to uphold basic standards of decency and honesty in public life, they have a just cause.

Carmichael has only a legally powerful but politically unattractive reply, playing on judicial caution. He is entitled to advance his defence. But come what may, Carmichael is now a damaged figure, his good name shredded.