Darby and two other officers were placed on leave at the time of the shooting, but a review board cleared them of any wrongdoing about a month later, Al.com reported.
The Alabama grand jury saw the case differently.
Under state law, a murder charge requires the element of "intent," meaning the defendant meant to kill the victim, according to WAFF.
Huntsville police Chief Mark McMurray said at a news conference Friday that Darby is on administrative duty pending the outcome of his trial.
In a statement, McMurray said Darby is “by no means a murderer.”
"Officer Darby was called upon to make split second decisions in a nightmare scenario, the likes of which most people will never experience," said McMurray. "His training allowed him and his fellow officer to survive as he rushed bravely, without hesitation, into one of the most volatile and unpredictable situations a police officer is called upon to face."
Madison County District Attorney Robert Broussard told WAFF his office had enough concern about the incident to present the case to a Madison County grand jury.
Friday’s grand jury indictment determined that there is enough evidence to formally charge Darby and send the case to trial.