Generally, before a person can be arrested by the police or any other law enforcement officer, such person must be issued a warrant of arrest. There may be some conditions that a warrant of arrest would not be needed. They include:
1. Where an offence is committed in front of a police officer, he can arrest the offender without a warrant. It would not matter that such offence if ordinarily committed would have required a warrant.
2. If a police officer has reason to suspect that a person committed an offence against any law within Nigeria or outside Nigeria, and the law creating such offence does not restrict arrest without a warrant, he would be allowed to arrest without a warrant.
3. In a situation where a person tries to escape from lawful custody or obstructs a police officer from performing his duty, he can be arrested without a warrant.
4. If a person in any of the armed forces of Nigeria deserts, he can be arrested without a warrant.
5. Where a person is found with any weapon or instrument of housebreaking, and cannot provide a lawful excuse, he will be arrested without a warrant.
6. Where a person is reasonably suspected of committing an offence outside Nigeria and such offence is considered unlawful in Nigeria, such person can be arrested without a warrant.
7. Where a person is suspected to be hiding in order to commit an offence, he can be arrested without a warrant.
8. Where a person is suspected of devising or hatching a plan to commit an offence, and such offence does not require a warrant of arrest in order to make an arrest. A police officer would be allowed to make an arrest without a warrant if that offence cannot be prevented.
9. Where a public summons is issued to a person and requires him /her to appear in accordance with any law, an arrest without a warrant can be made.
10. Where a person is in possession of stolen property or is reasonably suspected of committing an offence in respect of stolen property, he can be arrested without a warrant.