In a country once known for political interference in the judiciary, Kenya's Chief Justice Martha Koome is no pushover: she built her career defending dissidents, and this year her court torpedoed constitutional changes proposed by the president who appointed her.

But her own reputation for independence and fairness is on trial after opposition leader Raila Odinga filed a Supreme Court case on Monday seeking to overturn the results of the Aug. 9 presidential election.

The election commission is split: the chairman announced that Deputy President William Ruto won by about 233,000 votes, but four out of the seven commissioners dissented, saying results were not aggregated correctly. Kenya's largest civil society election observation group says its count supports the chairman.

Any perceived misstep in the ruling by Koome or the six judges she presides over could damage public faith in the judiciary and imperil the peaceful transfer of power in East Africa's richest and most stable nation.

The dispute has raised tensions in a nation with a history of deadly election disputes.

"We urge the judiciary to remain an impartial arbiter," the Angaza Movement, a Kenyan civic and human rights consortium, said on Friday, adding the "tranquillity and peace of the nation" depended upon it.

The stakes are also high for the judges themselves: when Kenya's Supreme Court nullified the 2017 election results, judges faced a torrent of abuse, were called "crooks" by the president and one of their bodyguards was shot and injured.

Koome, appointed in May 2021 by outgoing President Uhuru Kenyatta, has a reputation for integrity.

Months after her appointment, she quashed broad constitutional reforms backed by both Odinga and Kenyatta, which were widely seen as an attempt to sideline Ruto. Kenyatta fell out with Ruto after the 2017 elections and formed an alliance with Odinga.

Koome's ruling prompted praise even from critics like Ahmednasir Abdullahi, a lawyer who has frequently questioned Koome's independence and who supports Ruto.

"On the whole, good judgment by the Supreme Court," he tweeted, praising Koome and a second judge for being "outstanding in their reasoning".

CHALLENGING POWER

In 2017, the Supreme Court became the first African court to scrap the re-election victory of a sitting president, after it annulled on procedural grounds results giving Kenyatta a second term. Kenyatta won the rerun after Odinga boycotted it.

Four of those judges remain on the Court. The chief justice retired and Koome replaced him.

Koome - who has 34 years of legal experience - cut her teeth representing political detainees like Odinga when he protested against state repression in the 1980s and 90s.

In Odinga's stronghold of Kisumu, faith in the courts helps keep protesters off the streets.

"Many years ago ... courts seemed to be controlled by the government. But today's courts have come out to be more independent," said carpenter Meshack Nyamema.

Koome, 62, is already a trailblazer: her appointment made her the first female head of any Kenyan branch of government. She often discusses her Christianity and liberal social views.

One of 18 children from a polygamous family of subsistence farmers, Koome co-founded and chaired the Federation of Women Lawyers. It campaigns for women's rights, offers poor women free legal services and contributed to a landmark 2010 constitution that guaranteed women new rights.

In another departure from orthodoxy, in 2019 she supported a ruling that it was not illegal to identify as gay. Gay sex is punishable by 14 years in jail.

This May, Koome used a national prayer breakfast to warn against settling election disputes on the streets.

"I pray for those who might be tempted to divide our nation for their selfish reasons," she said. "This country belongs to everyone, and not just politicians."