Onuoha, 42, who is a former Exxon Mobil Engineer, was convicted on Monday.
Justice Adedayo Akintoye sentenced him without an option of fine.
On Jan 4, 2016, the state government had accused Onuoha of committing the offences at 11:30 a.m., at 25, Samuel Amoore Street, Idowu Estate, Ike-Ira Nla, Ajah, Lagos.
The prosecution led by Jide Martins said the defendant willfully had an unlawful sexual act with the teenager without her consent.
He said the offences contravened Sections 134 (2), 135 (1), and is punishable under Sections 137 and 258 of the Criminal Law of Lagos State, 2011.
Onuoha, however, pleaded not guilty to the charge.
The prosecution subsequently opened its case and called witnesses including the victim.
After the prosecution closed its case, Onuoha opened his defence and was led in evidence by the defence counsel, Dr Victor Olowonla.
After conclusion of witness testimony in January 2020, parties adopted their final written addresses and the court adjourned the case to March 25, for judgment. But the judgment could not be delivered owing to the COVID-19 pandemic which led to a lockdown in March.
At the resumed hearing of the matter on Monday, the court found the defendant guilty but before his sentence could be read, his counsel, Victor Olowonla, made his allocutus.
He said, ” My lord, the convict is a first time offender, he is a family man with wife and children and also the bread winner of his family.
“He has lost his job since this case came up, going by the circumstances of this case, I urge my lord to tender justice with mercy, ” Olowonla said.
Onuoha was first arraigned in January
2016 at the Magistrates’ Court on a four-count charge of defilement.
After his arraignment he was remanded at the Kirikiri correctional centre pending legal advice from the Director of Public Prosecutions (DPP).
Following his indictment by the DPP, the case was transferred to the high court for trial.
The Lagos State Government said the offences contravened Sections 134 (2), 135 (1), and is punishable under Sections 137 and 258 of the Criminal Law of Lagos State, 2011.