Dr. Abdulai Osman Conteh was born on 5 August 1945 in Pepel, Port Loko District. Raised mostly in Freetown, he attended the Albert Academy and later Fourah Bay College before travelling to the UK for further studies. Dr. Conteh has the following educational qualifications: Ph.D, (International Law), 1974, King's College, Cambridge; LLB (Hons): 1971, King's College, Cambridge; LLM: 1971, London University, United Kingdom; LLB (Hons): 1969, King's College London; Barrister at Law: Called to the Bar of England and Wales, 1970, at Lincoln’s Inn, London, United Kingdom; Harold Porter Prize man In Land Law, 1968. He returned home in the early 70s and worked for the SL Law Officers Department. Dr. Conteh later went into private practice and taught Law at Fourah Bay College for several years.
He is from the Susu people of Kambia, Sierra Leone, and was part of the All Peoples Congress (APC) party.
Dr. Conteh is married to Radia Labi Conteh and they have 6 children.
Conteh's public service in Sierra Leone has included holding the offices of Minister of Foreign Affairs (1977–1984); Minister of Finance (1984–1985); Attorney-General and Minister of Justice (1987–1991) and First Vice-President and Minister of Rural Development (1991–1992). He served as a member of Parliament from Kambia District (his paternal home district) from 1977 to 1992.
In late 2007, Conteh was nominated as a candidate to become Chairperson of the African Union Commission in early 2008, but he was not successful, with Jean Ping of Gabon being elected.
In January 2000, Conteh became the Chief Justice of the Belize Supreme Court.
In 2008 and 2010, Conteh authored two decisions affirming the common law doctrine of aboriginal title and the existence of Maya customary land tenure in the Toledo District of Belize. Only the villages of Conejo and Santa Cruz were parties to the 2008 ruling; however, the 2010 ruling was the result of a representative action on behalf of all the Maya communities. The ruling voided all government leases, concessions, grants, and contracts adverse to the Maya tenure. The "landmark victory" is predicted to have "far-reaching implications" for "logging, mining, and petroleum concessions in what the Maya community claims is over 500,000 acres of ancestral homeland." The government intends to appeal the decision to the Caribbean Court of Justice.
Conteh turned 65 on 5 August 2010, forcing him to retire since his contract was not renewed by Prime Minister Dean Barrow. Barrow's decision not to offer Conteh a renewal was condemned by the Belize Bar Association in a resolution criticising the "unseemly manner in which the tenure of the chief justice has been treated by the government of Belize." His retirement became a "national political issue because the Chief Justice is popular with the masses of the Belizean people, and is regarded by many as fair-minded and fearless. Several of his landmark rulings particularly on constitutional issues are considered "anti-government" and "anti-establishment," and many were made even under the former Musa administration."
In December 2008, Dr. Conteh was appointed as a Justice of the Court of Appeal of the Cayman Islands. In 2010, he was appointed to the Court of Appeal of the Bahamas.