The Supreme Court seemed split Tuesday on whether to require police to read Miranda rights to prison inmates every time they interrogate them about crimes unrelated to their current incarceration.

The high court heard arguments from lawyers from the state of Michigan who want a federal appeals court decision overturning Randall Lee Fields' conviction thrown out.

Fields was serving a 45-day sentence in prison on disorderly conduct charges when a jail guard and sheriff's deputies from Lenawee County, Mich., removed him from his cell and took him to a conference room. The deputies, after telling him several times he was free to leave at any time, then questioned him for seven hours about allegations that he had sexually assaulted a minor. Fields eventually confessed and was charged and convicted of criminal sexual assault.

Fields was then sentenced to 10 to 15 years in prison but appealed the use of his confession, saying that he was never given his Miranda rights on the sexual assault charges.

On appeal, the 6th Circuit Court of Appeals in Cincinnati threw out his confession and conviction, ruling that it is required that police read inmates their Miranda rights anytime they are isolated from the rest of the inmates in situations where they would be likely to incriminate themselves.

This case is another example of the courts' recent struggle to clearly define Miranda rights, which have been litigated since they first came into being in 1966. The courts require police to tell suspects in custody they have the right to remain silent and the right to have a lawyer represent them, even if they can't afford one.