Final answer:
If an officer discovers after an arrest that there is no longer probable cause, they must release the individual. Probable cause is a constitutional requirement for detention. Without it, the legal basis for the arrest is insufficient, leading to the necessity for release.
Step-by-step explanation:
When an officer makes an arrest but later discovers that probable cause did not exist at the outset, or that probable cause has since evaporated, the officer is generally required to release the arrested individual. This is because the legal foundation for the arrest no longer exists. The constitution mandates that probable cause is a prerequisite for detaining someone, thereby protecting individuals from unreasonable searches and seizures.
In a scenario where police apprehend individuals suspected of armed robbery but only have concrete evidence of unlawful weapon carriage, they may make an initial arrest based on probable cause. However, if subsequent investigations fail to provide the necessary evidence to support the suspicion of armed robbery, the stronger charge would lack probable cause. If the original basis for the arrest, the suspicion of armed robbery, is no longer substantiated, and no alternative justification such as new evidence of a different crime is found, the suspects should be released with regards to the specific suspected crime of armed robbery.
To sum up, probable cause is a critical legal safeguard, and its absence after an arrest necessitates re-evaluating the detained individual's situation. This often results in release unless other legal grounds for detention emerge.