Steve McNair's Murder Case Should 'Absolutely' Be Reopened, Ex-Cop Says

The new Netflix documentary on Steve McNair 's murder has left fans with more questions than answers ... and a former cop tells TMZ Sports that in order to fully get to the bottom of it all, police should now reopen the case.

The man who's desperately trying to figure out what actually happened to the ex-NFL star is Vincent Hill -- who briefly appeared in "Untold: The Murder of Air McNair," a Netflix doc that explored the life and death of McNair.

In the program, Hill -- a former Nashville Police Dept. officer who's since become a private investigator -- made a case that McNair might have been gunned down in his Tennessee condo by a male assailant ... not his mistress, Sahel "Jenni" Kazemi .

Hill openly questioned the Nashville Police Department's investigation ... and in an interview with us about the matter this week, he said he thinks cops were pressured into closing things too early because of McNair's celebrity status.

He argued that police should "absolutely" re-look into things to make sure they were right about their initial murder-suicide conclusion.

STEVE MCNAIR ON THE FIELD

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It's become such a hot-button topic since the doc dropped ... Hill says he's actually been approached by different filmmakers who want to hear him and his theories out further.

Hill went on to spell out some of those beliefs for us ... including what he believes happened on the night that McNair and Kazemi were found dead.