The Concept of Competency and Compellability of Witnesses

The Concept of Competency and Compellability of Witnesses by Nelson Vincent Ayomitunde

Competency is the mental ability to understand problems, make decisions and give evidence. It is the capacity to understand proceedings. On the other hand, compellability concerns whether a witness is obligated (or can be forced) to give evidence at proceedings even against his/her wish. 

The main issue of concern is whether a witness may legally give evidence in a judicial proceeding. It is not about the question of reliability. There are legal disabilities forbidding certain witnesses from testifying.  A good example is a child who by reason of his age cannot understand the question that are put to him or her or give answers that can be understood.
The general rule is that every person is competent to give evidence (Chapter XI Evidence Act, 2011) except: 

  • Persons of unsound mind and drunkards who are incapable of giving rational testimony.
  • A child in civil cases, too young to understand the nature of the oath. 
  • Persons who will neither take the oath, nor affirm.

All evidence must, as a general rule, be given on oath or affirmation. Oath is by swearing with the Holy Bible by Christians, the Holy Qur’an by Muslims and traditionalists. If a witness has no religious belief, or if the taking of an oath is contrary to his religious belief or if his religion permits him to take an oath but compliance with the  requirement of this religion would cause undue inconveniences or delay, he may not be comptent to testify. The following witnesses do not need to swear or affirm:

  • Children of tender years, who do not understand the nature of an oath, but who understand the duty of speaking the truth.
  • A witness, who is merely producing a document. 
  • A Counsel or a judge explaining cases in which he is previously engaged. 
  • An accused unsworn statement without cross examination either in lieu of or in addition to, his sworn statement. 
  • The Head of State, (not being foreign sovereign)

Any person or witness, who understands and can affirm an oath is competent to give evidence. In law and practice, any conviction based on the evidence of a witness who has not been lawfully sworn is bad. A competent witness may also be a compellable witness with certain exceptions (e.g spouses are not compellable witnesses for each other in a criminal proceeding.)

Competency of Children

The competency of a child to give evidence is determined by a test of intellect.  A child who does not understand the nature of an oath is incompetent to give evidence. The Children and Young Persons Act permits a young child, who does not understand the nature of an oath to give unsworn testimony if the judge is satisfied that he or she understands the duty of speaking the truth.  Such unsworn evidence of a child is not to be admitted or acted upon unless it is corroborated as no person can be convicted upon an uncorroborated and unsworn evidence of a child. In this context, the age of the child is not material, but the child must:  

  • Possess intellect
  • Fall within the definition of a child (a person under the age of 14 years).

To determine whether a child understands the nature of an oath (and therefore be competent to give evidence), the judge must examine the child in the open court.  

Competency and Compellability of witnesses

  • Witness for the Prosecution: The following are not competent as witnesses for the prosecution:
    • the accused person 
    • the spouse of the accused with certain exceptions 
    • persons jointly indicted or jointly tried with the accused 
    • spouses of persons jointly charged or jointly tried with the accused
  • Witness for the Defence: The following are competent witnesses for the defence 
    • The accused person whether charged solely or jointly. 
    • The spouse of the accused person

Rights   of   the   accused   person:  The   rule   as   to   competence   and compellability.
He is a competent witness for himself. His failure to give evidence is not subject to comments by the Prosecution. He may not be called as a witness, except upon his own application. If called, he may be asked any question in cross-examination, whether or not it incriminates him as to the offence charged.
He may not be asked and if asked shall not be required to answer any question tending to show that he has committed, or been convicted of, or  charged with, any other offence, or is of bad character unless:

  • Proof of the commission or a conviction for that other offence is admissible to prove the present offence as in evidence system.
  • He personally or by his counsel asked questions of witnesses for the prosecution with a view to establishing his own good character or has given evidence of his good character. 
  • The nature or conduct of the defence is such as to involve imputations on the character of the prosecutor or the prosecution’s witnesses.

By putting character in issue, an accused person puts the whole of his or her character in issue and may, as a general rule, be cross -examined with regards to previous charge for which he or she was convicted; to bring up evidence as to statements made at that trial, which tend to conflict with the evidence in the court trial. Also, it is not all the imputation made on the character of witnesses for the prosecution that may(not) put the character of the accused in issue. For example:
It does not in cases where: 

  • The attacks are directed at persons who are not parties e.g..
    • The presiding magistrate 
    • The police officer (or a police officer, who does not give evidence) 
    • The deceased
  • If defence merely denies the prosecution’s evidence however, vehemently.For instance, to say “The Police witness is a liar” is nothing more than “pleading not guilty with emphasis”. A cross examination of a prosecution in the case of rape or indecent assault to the effect that the prosecutrix consented is not an imputation on her character. 

Spouses of Parties

(a) Position of Accused’s Spouses:
After divorce, spouses become competent witnesses for the prosecution. They remain incompetent in respect of matters occurring during their marriage. However, if it is a decree of judicial separation, the spouse remains incompetent witness. Also, parties to a marriage that is void ab-initio are not affected by incompetency as there was never a marriage. The following cases are examples in which a spouse is not competent to give evidence for the Prosecution or the defence, without the consent of the Accused.
⦁    Neglect to maintain  or desertion of wife or family
⦁    Offence relating to children
⦁    Child destruction
⦁    Bigamy
⦁   Sexual offences other than bigamy, indecent assault on a man, and assault with intent to commit buggery.
d. Cases in which a spouse in both competent and compellable. These are:
⦁    Offences against the spouse’s property
⦁    Offences of violence against the spouse
⦁    Cases brought  for the purpose of enforcing civil rights (e.g. public nuisance)
The spouse is competent to give evidence against the other spouse in cases where the health, liberty, or person is involved. Thus a spouse is a compellable witness where the other is charged with attempting to strangle his or her, intent to murder him or her, causing grievous bodily harm, maliciously inflicting bodily harm or attempting to poison him or her with intent to murder. Cases in which the spouse is competent and/or compellable include attempt to commit such cases. These rules which apply to spouses, are applicable during the subsistence of the marriage between the spouses and after the termination of such marriage.  They apply to:
⦁    Spouses during the subsistence of marriage
⦁    Ex-spouses (i.e. erstwhile husband or wife who have divorced) for offences committed during the subsistence of the marriage.
⦁    Persons whose voidable marriage has been annulled.
In this, void marriage is no marriage and parties to it are not spouses. Conversely a marriage still subsists even after a decree of judicial separation.  Thus a spouse’s incompetence to give evidence against the other spouse is not brought to an end by a decree of judicial separation.
The sum total is that in civil court, both parties and their spouses are compellable witness.  The accused is never a compellable witness in criminal cases.  His spouse is neither competent nor compellable for the persecution.  For the defence, she is competent on the application by the accused but not compellable.


An accused is a competent, but not compellable witness in his or her own case or in defence of a co-accused.  He is not also a competent witness for the prosecution. The following are competent witness for the defence:
1.  The accused person, whether charged solely or jointly
2.  The spouse of the accused person.
Suppose after investigation, Police finds X and Z liable for conspiracy and X and Z were jointly charged X is competent to testify at the instance of Z and vice versa. Neither of them can be compelled and none can equally testify for the prosecution. However, if X and Z are charged separately. They cease to be co-accused and can be used one against the other. vIf  a  defendant  fails  to  give  evidence  in  his/her  own  defence  (if  when  giving evidence,  refuses  without  good  cause  to  answer  any  question),  the  court  in determining  whether  he/she  is  guilty  of  the  offence  charged,  may  draw  such inferences from that failure as may appear proper. 

Securing Attendance

The following forms or processes are available for securing the attendance of witness:
⦁    The Magistrate’s Courts. Witness Summons: In the Magistrate’s Courts, a witness summons may be issued to compel a witness attendance.  The witness is entitled to be paid money or travelling expenses.
⦁    High Court. Attendance of witness may be enforced by:
1. Subpoena ad testificandum – This requires the witness to attend and give oral evidence.
2. Subpoena duces tecum – This orders the witness to bring and produce a document.
3. Habeas corpus ad testificandum – This orders the custodian of a person imprisoned in consequence of a civil process to produce the prisoner to give evidence.
4. Judges  Order  –  This  is  used  where  the accused is  in prison awaiting  trial  or  under sentence.

  • In criminal trials a child who understands the question asked or able to give a rational answer is competent. 
  • Persons of unsound mind, by reason of the defect in their intellect, cannot be a competent witness.

A witness is competent if he or she possesses the mental ability to understand the proceedings and make a decision.  He or she is compellable if there is an allegation to give evidence. Spouses and children occupy special positions, the law of evidence has specified cases where they are competent, but not compellable or where they are both competent and compellable. So, every person charged with an offence, shall be competent witness for the defence provided:
⦁    He elects upon his own application
⦁    Failure to give evidence shall not be subject to comments
⦁    He may be asked any question in cross examination notwithstanding that it would tend to criminate him as to the offence charged.
⦁    He shall not be asked and if asked, shall not be required to answer, any Question tending to show that he or she committed or been convicted of or been charged with any offence other than that wherewith he is then charged or is of bad character.
⦁    It is to show that he is guilty of the offence charged.
⦁    He  asks  questions  with  a  view  to  establish  his  own  good character.
⦁    He has given evidence of his good character
⦁    Nature of conduct of defence involves imputation on the character of the prosecutor or his witness.
S 180, Evidence Act, and  429 and 250 of  the  Criminal  Codes.  

The following persons are competent but not compellable:

  • Head of State
  • Ambassadors
  • governors
  • wife of an accused
  • Competency of a child - Okon v. State, Okoye v. State, Summonu v. Police
  • Competency of an accused person - An accused cannot give evidence against himself (Sambo v. State). He may choose to be silent
  • competency of a dumb - Evidence can be given by signs or in writing so the dumb is not incompetent. Whichever way, the signs or written document must be in open court.
  • Competency of Spouses - the two (couple) are deemed by law to be one, so they can't testify against each other. In criminal cases though, spouses can be compelled to witness against each other
  • Competency of a lawyer- A lawyer being a natural person may give evidence, however not in a case wherein he defends or prosecutes.

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