The claim of "marital coercion" used by Vicky Pryce is a rarely-used defence that has come under attack for being out-of-date in 21st century society.
The ancient defence in its current form dates back to 1925 and relies on the husband's physical presence at the time that a crime has been committed. It can be used for any offence other than treason or murder.
However, the defence is not available for husbands or civil partners and changes to the law surrounding gay marriage are likely to see the measure either scrapped or drastically changed in the future, according to lawyers.
"The idea that someone's criminal liability depends on whether they are man or woman or within a marriage or long-term cohabitation is, to all modern sensibilities, absurd," said Andrew Edis, QC during arguments not heard by the jury.
The last known use of the defence was in the case of the wife of John Darwin, the man who faked his own death - and tricked his own family into believing that he had died while out canoeing - in order to claim an insurance pay-out. Anne Darwin's attempt in 2008 to claim the defence was thrown out after it was shown that she had exchanged loving emails with her husband. She was jailed for more than six years.
Dean Armstrong, a member of her legal team, said despite the changes to society there were good reasons for keeping it. "Before it disappears, I think we will have to think very, very carefully. Are we taking away potential situations where justice demands this defence is available to a wife?"
Vicky Pryce's use of the defence depended on Chris Huhne being present at the time she signed the forms confirming that she was a driver of the car in 2003. She told the court that it "was one of my strongest memories of this whole sad affair, him standing at the hallway table, lots of papers around and the form, and being made to sign."
The prosecution suggested that she had made up the episode to allow her to use the defence. Andrew Edis, QC, prosecuting, said that she had not mentioned it during six "no comment" interviews with police.
Two people whom Ms Pryce confided in about the pressure she was under, her eldest daughter Georgia and Isabel Oakeshott, the political editor of the Sunday Times, both said that they did not recall her telling them about the hallway incident when they gave evidence at the trial.