By Matthew Mpoke Bigg
ACCRA (Reuters) - Ghana's Supreme Court said on Wednesday it will rule by August 29 on an opposition challenge to the result of December's presidential election that was won by incumbent John Mahama.
The outcome could have big implications for the West African state where investor excitement over its strong economy - GDP is expected to grow by 8 percent in 2013 for the second consecutive year - is tempered by concern over macroeconomic instability.
Justice William Atuguba told a packed court during closing arguments in the case that the panel of nine judges would issue its verdict 15 days after a further hearing due on August 14.
Four lawyers involved in the case said they understood the statement to mean a ruling would be issued on or before August 29 on an election that was the first in Africa to use biometric data for voter registration.
Opposition leader Nana Akufo-Addo has challenged the outcome of the poll, claiming Mahama's slim 50.7 percent victory was tarnished by irregularities in the election data and that he would have won if only valid ballots had been counted.
"These malpractices and irregularities have a material effect on the result," Philip Addison, a lawyer for the opposition New Patriotic Party, said during a 30-minute address summarizing for the court months of often arcane legal arguments.
Mahama's lawyer Tony Lithur said the NPP had failed to back up in court its claims in the immediate aftermath of the election of "planned systematic stealing of votes".
"The petitioners are asking you to impose a retroactive penalty on people (voters) who stood in line for hours," Tsatsu Tsikata, counsel for the ruling party, told the judges.
STATUS QUO FORECAST
Political stability and a record of peaceful elections underpin investor confidence in Ghana, which is booming on the back of exports of gold, oil and cocoa, and politicians and observers say they expect public order to be maintained when the court announces its verdict.
"If the court rules in favor of a new election, which seems unlikely, past track record suggests it would not result in a significant increase in political instability," said Carmen Altenkirch, a senior analyst at Fitch Ratings.
"The cost of running an election less than a year after the last and the risk of a repeat of fiscal loosening seen in 2012 (would be a concern)," she said, referring to a spike in the budget deficit to 12.1 percent of GDP last year.
While the case has exposed voting irregularities, the verdict will likely validate the election result, said lawyers and political analysts interviewed by Reuters.
Several said they expected a 6-3 split among the judges against Akufo-Addo with strong recommendations for electoral reform, though they stressed it is impossible to know which way the judges will rule.
"The electoral commission has been effectively audited ... so we all know what ... went wrong," said Kofi Bentil, vice president of the Imani Center for Policy and Education.
"The easiest way out (for the judges) is to maintain the status quo," he said.
The case will set a precedent for Africa because it provides an intensive audit of an election by a court widely perceived as neutral, said Afia Asantewaa Asare-Kyei of the Open Society Initiative for West Africa.
"I do think it's going to take a lot from the court to overturn the electoral result," she said.
(Additional reporting by Kwasi Kpodo; Editing by Joe Bavier and Paul Simao)