In 2010, she was one of the candidates considered by the Judicial Services Commission, for appointment as the chief justice of Uganda.
In 2006, she dismissed the petition in which the National Resistance Movement’s Francis Babu had challenged Erias Lukwago’s victory as member of Parliament for Kampala Central Division.
In 2012, at the Court of Appeal, she wrote the majority opinion that nullified NRM's Faisal Kikulukunyu's victory as the member of Parliament for Butambala County.
The ruling benefited Muhammad Muwanga Kivumbi of the Democratic Party.
[2] Arach-Amoko was married to Ambassador Idule Amoko who, as of April 2019[update], was serving as the Deputy Head of Mission at the Uganda Embassy in Addis Ababa, Ethiopia.