When can a suspect be compelled to testify?

A suspect can be compelled to testify in a court of law when they are granted immunity, meaning they cannot be prosecuted based on their testimony. Additionally, if the suspect is a witness in a case where their testimony is essential, the court may require them to testify, although they can still invoke their Fifth Amendment right against self-incrimination if their testimony could incriminate them. Ultimately, the specifics depend on jurisdiction and the circumstances of the case.