This story was edited to correct an error. Cobbins' motion was not filed Thursday, but rather filed previously and argued Thursday.

KNOXVILLE, Tenn. (WVLT) -- There were big questions Thursday in a Knoxville courtroom as to what, if any, involvement Vanessa Coleman had in the murders of Channon Christian and Christopher Newsom in January 2007.

Coleman and three others are charged in the rapes, torture, and slayings of the couple.

A document written by a federal prosecutor in the early days of the investigation states that there was no evidence Coleman participated in the crimes.

The document was filed along with a request for immunity for Coleman to testify in the federal trial.

Prosecutors contend the document was filed too early in the investigation to know that for sure, and all the evidence wasn't revealed yet.

Also Thursday, Letalvius Cobbins arugued a motion to subpoena Coleman to testify at his trial.

Judge Richard Baumgartner has yet to rule on either motion.

Another hearing is set for May 22.