Perverting the course of justice carries a maximum sentence of life imprisonment, although the average sentence is around 10 months.
Both 58-year-old Chris Huhne and economist Vicky Pryce, 60, have been warned to be under no illusion about what punishment they face.
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The vessel went missing last week with 44 sailors on board.
Joined by 18 Labour MPs, McDonnell voted with 283 Conservatives, eight DUP and two independents to defeat the Taxation Bill amendment.
Gerry Adams has told UTV the “time is right” for him to step aside as president of Sinn Féin, after announcing that he would do so in 2018.