A Nigerian opposition candidate is appealing to the Supreme Court over the election of President Umaru Yar'Adua.
Muhammadu Buhari says the tribunal was wrong
Defeated All Nigeria People's Party candidate Muhammadu Buhari wants last year's widely criticised poll annulled.
Last week, the election tribunal said Mr Buhari had failed to prove the result of the election had been affected by rigging.
Mr Buhari's lawyers said the burden of proof should be on the government.
During the tribunal he provided bags of evidence the electoral act had been broken.
Serial numbers allowing auditors to create a paper trail, were missing from ballot papers.
Result sheets from local wards did not match results announced in the capital Abuja, and in some areas where people reported they were not able to vote, 100% turn outs were recorded, Mr Buhari's lawyers said.
But lawyers acting for the country's election regulator pointed to weaknesses in his case.
For example all the witness testimonies filed by Mr Buhari's lawyer Mike Ahamba, about the election in Imo state were friends from the lawyer's home village, the tribunal heard.
International observers said the April polls fell short of expected standards.
The 2007 election saw the first transfer of power from one elected leader to another in Africa's biggest oil producer and most populous country.
The official results show that Mr Yar'Adua gained more than 70% of the vote, compared to 18% for Mr Buhari and 7% for Atiku Abubakar.
Neither opposition candidates claim to have actually won the election - they had called for a re-run.
Mr Yar'Adua has admitted there were flaws in the vote and has promised to reform the electoral system before the next elections.
Mr Buhari, who also contested the previous election in 2003 and is a former military ruler of Nigeria, maintains the vote did not take place in 29 of the 36 states.