Steve McNair's documentary examines questionable police investigation into a murder case

A new Netflix documentary “Untold” questions the investigation into the death of former NFL star Steve McNair.

McNair was 36 when he was shot and killed in his downtown Nashville apartment on July 4, 2009.

Nashville police determined he was killed in a murder-suicide by his girlfriend, Sahel “Jenni” Kazemi.

Fifteen years later, it's still unclear whether police thoroughly investigated the case, and those close to McNair, the 2003 NFL MVP and three-time Pro Bowler, still wonder what the true cause of death was.

“I think once people start seeing the gaps, the holes and the things that don't make sense in this case, anybody with common sense will say, 'Wait a minute, guys, you screwed up,'” Vincent Hill, a private investigator who wrote a book criticizing the police portrayal of the killing, said in the documentary.

Investigators found that Kazemi, a 20-year-old waitress at Dave & Buster's, was the one who shot McNair first and then herself after finding a pistol underneath her and gunpowder on her hand.

Police discovered that the couple had been having relationship problems in recent days. Additionally, Kazemi had been arrested for drunk driving two days before her death. Further evidence led police to conclude that she had killed McNair and herself.

But Hill claims the case was not that simple.

“The Nashville Police Department made a lot of mistakes,” Hill said.

The biggest mistake, Hill claims, was believing the story of Adrian Gilliam, who claimed to have barely known Kazemi before selling her the gun used in the murder, which was registered in his name.

During an interview the day after the murder, police discovered that Gilliam had indeed had a close relationship with Kazemi. Police records show that they had spoken on the phone more than 200 times in the weeks before the murder, including once just after midnight on the day of her death.

These initial untruths should have set off alarm bells for investigators at the time, Hill said.

“Adrian Gilliam lied about where he was at the time of the murders,” Hill said. “He lied about how often he was in contact with Jenni. His alibi is that he was shot, he was the last person to call her, [and] it's his weapon. It's not rocket science.”

Hill also investigated the actions of McNair's longtime friend Robert Gaddy.

Gaddy and another friend, Wayne Neely, discovered the bodies.

Gaddy reportedly had an argument with McNair over $13,000 before the murder and was the one who called 911 at the apartment.

In an interview in the documentary, lead investigator Charles Robinson denied the allegations and questioned Hill's credentials.

“Ask him about his resume. “… How many murders has [he] “Work for the police?” said Robinson.

“Zero. And [he] was not even active as an investigator when [he] left the police force. His first investigation was, guess what, Steve McNair.”

Former Titans head coach Jeff Fisher, who coached McNair for 10 years in Houston and Tennessee, including a Super Bowl run with the Titans in 1999, declined to make assumptions during his appearance on the documentary.

“I can argue that this doesn't add up,” Fisher said. “… I don't want to speculate. Just let it go. Let it go.”