The Iowa Supreme Court announced it will hear a case relating to an alleged material witness in an Iowa City murder trial.

Justin Marshall, 20, was held in jail for months after police said he witnessed the October 2009 shooting death of John Versypt, the landlord of an apartment building on Broadway.

Police eventually arrested Charles William Curtis Thompson for the alleged shooting. He is set to be tried in September.

Marshall was never charged with a crime in connection with the case, but, according to court documents, police believed Marshall had key information regarding details of the shooting.

None of the lawyers in the case could be reached for comment Wednesday night.

The material-witness law allows authorities to hold people they believe have information vital to their case, experts said. But the law is controversial, and the wording sometimes unclear, so Johnson County prosecutors hope the Supreme Court can clarify the breadth of the statute.

The Supreme Court will hear Marshall’s case May 19 in Cedar Rapids.

Johnson County prosecutor Janet Lyness said there is a discrepancy in the interpretation and language of the law, noting a subpoena alone will not force someone to stay in the state during the case.

“If we have reason to believe they’re going to flee, just giving them a piece of paper isn’t going to keep them to testify,” she said.

Tim Hagle, a University of Iowa political-science associate professor, said there is always a risk a witness will not want to testify in a case, particularly in more serious cases, such as murder.

“The general idea here is that there may be some people that have information that’s relevant to the prosecution, but they might not want to testify,” Hagle said, noting gang-related issues or possible family or friend connections as examples.

But law-enforcement officers are allowed to hold a material witness if he or she has information important to a case and if prosecutors believe that the person will flee.

“The idea is that [holding a witness] serves the greater good of making sure someone who has been accused of a crime would be punished, would get convicted,” Hagle said.

But the law has been questioned because of occasional abuses, said Ronald Carlson, a professor of law at the University of Georgia-Athens.

“If it’s very narrowly applied, then it’s OK,” the former UI law professor said. “Where I do see abuses sometimes is a fairly casual attitude by law-enforcement officials where they say there are alternatives, but it’d be nice to have [the witness] around for the trial.”

Carlson said he would encourage law enforcement to seek out the witness’s deposition, rather than automatically holding her or him in jail — which is the more common practice.

Proper law also requires a witness to be confined separately from the defendant, but this rule is not always followed, Carlson said.

“Sometimes, [the witness] is locked up along with the defendant they’re testifying against,” he said. “It’s a horrible situation when it does happen.”