The panel on Staten Island heard testimony last week from a police officer involved in the chokehold death of Eric Garner. He was believed to be the last witness.
The Staten Island district attorney won't comment on the proceedings that will determine whether the officer will face criminal charges. But an announcement is expected before the end of the year.
On Saturday, Rev. Al Sharpton held a rally in Harlem with Eric Garner's family planning protests in the aftermath of the looming ruling.
"We're looking for justice for my husband," Esaw Garner said. "It's not a black and white issue, it's a justice issue," she said.
Garner died during an arrest July 17. A widely watched amateur video shows one of the arresting officers wrapping his arm around Garner's neck before Garner lost consciousness.
The medical examiner found that the chokehold contributed to the death.