Onnoghen was born on December 22, 1950 at Okurike town, Biase local government area of Cross Rivers state.
After obtaining a law degree from the University of Legon, Ghana, he started his career as pupil state counsel at the ministry of justice, Lagos in 1978.
He practiced law for several years before he joined the bench.
He made history in Nigeria on April 11, 2014 when he, alongside some of his colleagues, made a landmark pronouncement in the case of two Igbo women, Gladys Ada Ukeje and Maria Nweke, who argued that they should have equal access as men to the inheritance of their parents.
In Igbo culture, women had been disinherited for ages as a result of tradition.
The two women sued the men in their families – and finally got justice as the case moved from the lower to the highest courts in the land.
He also upheld the death sentence meted out to Chukwuemeka Ezeugo, known as “Rev. King”, the general overseer of Christian Praying Assembly, who was accused of murdering a member of his church in 2006.
Futhermore, it was Onnoghen, who annulled Yar’Adua’s election in December 2008 and called for a fresh one, after the then Gen. Buhari argued that the election was rigged.
However, his decision, alongside other colleagues, did not hold as they did not have the required number of Justices to pull the judgement through.
Onnoghen is remarkably the first southerner to be CJN since 1987 when Ayo Irikefe retired, the cable revealed.