Ruggles v. Illinois was a case in which the Supreme Court of the United States ruled that an individual cannot be convicted for refusing to answer questions posed by police officers without violating their Fifth Amendment right against self-incrimination. The defendant, William Ruggles, had been arrested and charged with publishing obscene material after he refused to answer questions about his involvement in distributing such material. The court held that forcing someone to incriminate themselves violated their constitutional rights under the Fifth Amendment and overturned Ruggles' conviction on those grounds. This ruling established an important precedent protecting individuals from being forced into providing information or evidence against themselves during criminal proceedings.

In Ruggles v. Illinois, the Supreme Court was asked to determine whether a criminal conviction obtained in violation of an individual's right against self-incrimination could be used as evidence in a subsequent prosecution for perjury. The majority opinion held that such evidence was admissible and did not violate the defendant's constitutional rights. However, Justice Field dissented from this decision on two grounds: first, he argued that allowing such evidence would lead to "the destruction of all security for personal liberty," since it would allow prosecutors to use illegally obtained convictions as leverage against defendants; second, he argued that even if the original conviction had been legally obtained, using it as proof of guilt in another case violated double jeopardy principles by punishing someone twice for the same offense. As such, Justice Field concluded that any conviction based on illegally procured testimony should be excluded from consideration at trial and overturned if already admitted into evidence.