As reporters wait, tweet-fingers poised, for such nuggets of information as Rebekah Brooks may dangle before MPs this afternoon, constitutional lawyers will be much more interested in any excuses she may give for not answering questions.

Will she, for example, argue that the Commons media committee should not question her about allegations that she was involved in phone hacking or corruption because that would create a "substantial risk that the course of justice... will be seriously impeded or prejudiced" in her case?

After all, the Contempt of Court Act 1981 — from which that definition is taken — makes it clear that proceedings are "active" from the moment a person is arrested. And Brooks was arrested on Sunday.

It would be ironic if she were to accuse MPs of thwarting her right to a fair trial. Newspapers for which she was responsible published prejudicial information about suspects after they were arrested by the police. The tabloids often acted as though the publicity shutters did not come down until a suspect was charged — which Brooks has not been.

And there is no risk that MPs would face contempt of court proceedings by questioning Brooks about these issues. Though they would be expected to show proper respect for the legal process, any questions they put to her will be protected by parliamentary privilege.

Need she answer? In the United States, she might "take the Fifth", the constitutional right against self-incrimination.

In the UK, she can rely on article six of the human rights convention, the right to a fair trial. In 1996, the European court ruled that this right had been breached by legislation under which the former Guinness chief Ernest Saunders had been required to answer incriminating questions.

But the fact that Brooks has been arrested makes no difference. She can rely on article six in exactly the same way as the unarrested Rupert Murdoch and his son James can. Having a foreign passport does not deprive you from the protection of article 6, just as it does not exempt foreigners from having to comply with a select committee summons.

And yet, how would "taking article six" look? Refusing to answer MPs' questions on the ground that replying could incriminate might prompt the question "What has he or she got to hide?"

Any other means of avoiding the committee's questions? Brooks is bound to have a confidentiality clause in her pay-off deal with News International. But that won't help either, according to Tom Flanagan, head of employment at the law firm Irwin Mitchell.

"If a court of competent jurisdiction requires you to disclose information, then you must disclose it," he said yesterday. "The compromise agreement can't override that. A select committee inquiry would have this power."

What, though, if a witness deliberately gave untruthful answers to a parliamentary committee? Might that amount to contempt of parliament?

Arguably, it would — but nobody can be sure because this is an open-ended concept. Erskine May, the textbook of parliamentary procedure, says "any act or omission which obstructs or impedes either House of Parliament in the performance of its functions, or which obstructs or impedes any Member or officer of such House in the discharge of his duty, or which has a tendency, directly or indirectly, to produce such results, may be treated as a contempt even though there is no precedent of the offence".

There is no doubt that select committees have the power to examine witnesses. They also have a duty to report their findings to parliament. Telling lies to a select committee must surely impede that duty.

In the Commons last Thursday, the Conservative MP David Ruffley asked why, in modern times, parliament had not used criminal sanctions against witnesses who lied to select committees.

Sir George Young, leader of the commons, replied that a contempt of parliament could be referred to the standards and privileges committee. "If that committee finds that there has been a contempt, it has at its disposal a wide range of penalties, including fines," Young said, although he later made it clear that sanctions were ultimately a matter for the commons itself.

But there is no suggestion, of course, that anyone giving evidence to parliament later today will tell lies. So it looks as if constitutional lawyers will just have to confine themselves to academic theorising for a little bit longer.