The High Court in Kerugoya has for the second time dismissed a poll petition filed by Narc-Kenya leader Martha Karua against the election of Kirinyaga governor Anne Waiguru.
Justice Lucy Gitari also slapped Ms Karua with Sh5 million costs. She will pay Ms Waiguru's lawyers Sh3 million and those of the electoral commission Sh2 million.
Following the verdict, Ms Karua said she would appeal the decision.
"It is not over. We are determined to pursue justice to the last mile," she said outside the court.
The court ordered the deputy registrar to serve her with certified copies of the case proceedings.
While delivering the judgement on Thursday, justice Gitari said the election was free and fair.
"The results declared by the Independent Electoral and Boundaries Commission reflect the sovereign will of Kirinyaga people," the judge said after reading the decision for four hours.
She ruled that Ms Karua together with her eight witnesses failed to prove allegations illegalities and irregularities marred the election. The judge added that the claims such as voter bribery and exclusion of her agents from polling stations were unsubstantiated.