Which of these is a violation of someone's Fifth Amendment rights?

Forcing someone to testify against themselves is a clear violation of the Fifth Amendment rights. The Fifth Amendment includes the guarantee against self-incrimination, meaning that an individual cannot be compelled to provide testimony that could incriminate them in a criminal case. This protection is crucial in maintaining the principle that a person is presumed innocent until proven guilty and safeguards against coercion in legal proceedings.

In contrast, the other scenarios, while they may relate to rights protected under different amendments, do not directly pertain to the self-incrimination protection provided by the Fifth Amendment. Detaining someone without cause infringes on the Fourth Amendment's protection against unreasonable searches and seizures, while searching someone's property without a warrant also violates the Fourth Amendment. Imposing a fine without trial raises issues pertaining to due process, which is a component of the Fifth Amendment but does not specifically address self-incrimination like the forced testimony scenario does. This distinction highlights the specific nature of the rights protected by the Fifth Amendment.