Your surprise is well founded. While it is true that prosecution of violations of the laws of the land are fought as public fight through the prosecution and punishment of the violators through the public offices mentioned, it does very rarely happen that under some strict conditions, a private person can lawfully institute and prosecute criminal trials. The power to do that is given under Sections 342 of the CPA, 143 of the CPC, and for Lagos State, Section 254 of the Administration of Criminal Justice Law of Lagos State. For a private person to institute a criminal proceeding in the Southern States of Nigeria pursuant to S. 342 of the CPA, he would need to:
Obtain an endorsement on the Information sheet by a Law Officer certifying that he (the law officer) has seen the Information and has no intention of prosecuting the offence on behalf of the public;
Enter into a recognizance in the sum of N100 only together with one surety in like sum, undertaking to prosecute the matter with due diligence. And if it is in Lagos State, he further
Enter into Recognizance in the sum of N10,000.00 as set out under S.254(b) ACJL of Lagos State, 2011.
It is a bit differently done in the Northern States of Nigeria under Section 143(e) of the CPC wherein all the private person needs to do is to present the Information to the Court, which taking recognizance of the Information from the private person other than a Police Officer, sees reason to believe or suspect that an offence was indeed committed, takes steps to commence the prosecution of the accused person. In the Northern States, under the CPC, there is no requirement of recognizance or surety or any money deposit.
It is important that I add that while the Constitution does not burden the Attorney-General with the task of endorsing private information for prosecution of offenders, a private person can actually, in another way, ensure that an offence which the A.G. and the police are not interested in prosecuting gets prosecuted,. He can so by a court Order of Mandamus that compels the A.G. to prosecute a suspect. See Fawehinmi V. Akilu (1987) 11 – 12 SCNJ 151 and A.G. Anambra State V. Nwobodo (1992) 7 NWLR (Pt. 256)11
Also note that the old order formerly operative in Lagos State whereby a private person can prosecute only offences of perjury and other non-indictable offences as was held in Attake V. Mene-Afejuku (1996) 3 NWLR (Pt. 437) 483, has been altered by the entry of the ACJL of Lagos State, 2011 which has enlarged this right to cover all offences as long as the requirements in Sections 77(1) and 254 of that law are satisfied.