(CNN) Hours before Marcellus Williams was set to die Tuesday night, Missouri Gov. Eric Greitens issued a stay of execution and said he would appoint a board to review the evidence in the 1998 stabbing death of former reporter Felicia Gayle.

New DNA evidence that was unavailable during Williams' 2001 murder trial proved he did not do it, his attorneys said.

Felicia Gayle was stabbed to death more than 40 times in 1998.

But the Missouri attorney general's office wanted the execution to go ahead, arguing that evidence other than DNA linked him to the crime.

Here are key things to know about the governor's review board:

Who will be part of the board?

The board will have five members appointed by the governor, and will include retired state judges.

How common is such a board?

It's not.

Greitens cited a state law rarely used that allows him to appoint a board to review old and new evidence and report back to him.

"The governor may, in his discretion, appoint a board of inquiry whose duty it shall be to gather information, whether or not admissible in a court of law, bearing upon whether or not a person condemned to death should be executed or reprieved or pardoned, or whether the person's sentence should be commuted," the law states. "... Such board shall make its report and recommendations to the governor."

The appointment of a board of inquiry was last used in the 1990s by Gov. Mel Carnahan, according to the St. Louis Post-Dispatch.

Will the proceedings be open to the public?

No.

All the proceedings will be held behind closed doors, and information gathered will be kept in strict confidence, the governor said . The board will report the recommendations only to him.

"All information gathered by the board shall be received and held by it and the governor in strict confidence," the law states.

Will the board have subpoena power?

Yes.

Board members will have the ability to subpoena people and also apply to the circuit county court and other court jurisdictions for subpoena power, the governor said in his executive order.

How long will the review take?

While it's unclear how long the review will take, a spokesman for the governor said the stay will remain in place as long it's necessary for the review and governor to make a final decision.

The death row inmate's son, Marcellus Williams II, expressed joy at the stay and said he hopes it will lead to his father's exoneration.

"I'm happy that they took a second look because that really don't happen a lot," he said. "Got a fresh start, got a chance. My father got a stay in the eleventh hour on the day of execution. We were a couple hours out; they had everything set up."

The family will keep fighting to prove he's not guilty, he said.

"That's the ultimate goal, and that's what we are pushing for and that's what we want," the son said.

Why did the governor appoint the board?

Greitens defended his decision to issue the stay.

"A sentence of death is the ultimate, permanent punishment," he said in a statement. "To carry out the death penalty, the people of Missouri must have confidence in the judgment of guilt."

Gayle's widower, Dan Picus, is declining interviews, according to his wife.

Gayle was stabbed 43 times inside her home. New evidence shows DNA from another man, not Marcellus Williams, was on the murder weapon, according to the inmate's attorney.

That evidence was not available when Williams went to trial in 2001, according to court documents. Williams maintains he is not guilty and said he was convicted based on the testimony of felons.

The state attorney general's office said the new DNA evidence does not show that Williams is innocent. His guilt was proven without DNA evidence, it said.

In a statement, St. Louis County Prosecuting Attorney Robert P. McCulloch said he is confident a review of evidence will lead to the same conclusion a jury reached 20 years ago in its guilty verdict.