An accused upon arraignment is expected to plead any of the following;
a) Preliminary objection; it may relate to the jurisdiction of the court to try him or to a defect in the charge. His objection shall be duly considered and may be upheld or discharged on its merits.
b) Refusal to plead: The court shall enquire for his reasons. Where the court is of the view that those reasons are not valid and the defendant still refuses to plead, "a plea of not guilty" shall be entered on his behalf and the trial shall proceed. See Gaji v. The State (1975) See S.276 ACJA, S.215 ACJL Lagos.
c) Stand mute: He may stand mute, and the court shall call evidence to determine whether his muteness is of malice or due to the visitation of God. If the Court finds that his muteness is of malice, a plea of not guilty shall be entered and the trial shall proceed. See Yesufu v. The State (1972). However, if his muteness is of the visitation of God (e.g. insanity) the trial shall not proceed, and the defendant shall be ordered to be detained until the pleasure of the Governor is known. See R. v. Ogor (1961)
d) Plea of guilty: The guilty plea shall be recorded by the court and where the defendant intends to admit the truth of the essentials of the offence, it may convict him on such a plea. See S.274 ACJA, S.213 ACJL Lagos. See also Aremu v. The COP (1980)
e) Plea of not guilty: It is a denial by the defendant that he did not commit the offence he’s charged with. In such a circumstance he joins issues with the state. See S.212 ACJL Lagos, S.273 ACJA.
f) Plea of not guilty by reason of insanity; The court shall proceed with trial and determine: (a) whether the defendant did commit the offence; and (b) whether he was insane at the time of committing the offence. If he is found to have committed the offence and to be insane at the time of committing it, he shall be remanded in prison custody until the Governor's pleasure is known. See R. v. Ogor (1961)
g) Plea of autrefois acquit or autrefois convict: This plea is hinged on section 36(9) of the Constitution, that: "No person who shows that he has been tried by a competent court for a Criminal offence and either convicted or acquitted shall again be tried for that offence or for a criminal offence having the same ingredients as that offence, save upon the order of a superior court". See also 277 ACJA, and 216 ACJL Lagos.