Nigeria gets 'illegal' new chief justice
Nigeria's new chief justice has been sworn in in the absence of President Umaru Yar'Adua, who is in hospital in Saudi Arabia with a heart condition.
A lawyer has told the BBC that the appointment of Aloysius Katsina-Alu is illegal, as only the president has the power to take his oath of office.
Instead, the ceremony was presided over by outgoing Chief Justice Idris Legbo Kutigi, who retires on 31 December.
There have been several calls for Mr Yar'Adua to resign over his ill-health.
Senior lawyer Bamidele Aturu told the BBC that the constitution makes it clear that the chief justice can only be sworn in by the president.
"This means the legality of the appointment is in question and people can go to court and challenge it," he said.
But this was denied by Mr Kutigi, who said a law had long been in existence to allow chief justices to swear in their successors.
The Nigeria Bar Association has called for an independent medical assessment of whether Mr Yar'Adua is well enough to carry out his duties.
| The appointment of a person to the office of Chief Justice of Nigeria shall be made by the President on the recommendation of the National Judicial Council subject to confirmation of such appointment by the Senate |
Nigeria's constitution, Chapter VII, Section 231 - (1)
Last week, an opposition politician began legal proceedings to try to force President Yar'Adua to step down on health grounds.
He has been in Saudi Arabia for more than a month.
The BBC's Caroline Duffield in Lagos says no-one knows who is making decisions and there has been barely concealed panic among officials in Abuja over what to do about the retirement of Nigeria's most senior judge.
There was talk of flying the new chief justice to the president's bedside and filming a ceremony.
Instead, officials decided that the outgoing chief justice would perform the president's job.
They are relying on the Oaths Act, which says that any lawyer can take an oath from anyone else.
But many observers are warning that Nigeria's constitution is being kicked aside.
Mr Yar'Adua also failed to appoint his deputy acting president when he left - another constitutional requirement.
Doctors say the president is suffering from acute pericarditis - inflammation of the lining of the heart.
He also has a long-standing kidney complaint.