Famed civil rights lawyer Ben Crump just unveiled the lawsuit, and the stakes are enormous. The family is suing the 4 officers who are now criminally charged with Floyd's death.

The reality is this ... the officers don't have the kind of money that typically makes a civil lawsuit worthwhile. Enter the City of Minneapolis, which actually has limited immunity in these cases, meaning it can't be sued UNLESS it's approved the policy either explicitly or by way of custom.

Crump says in the lawsuit ... the City long trained its officers to use neck restraints, claiming they were an "authorized form of non-deadly force."

The fact is this ... it's simply not true that it's non-deadly force, and the City would have to be blind not to know that. Fact is ... the technique has been used since 2012 on 428 people nationwide, and 14% lost consciousness. And, if City officials turned on the news, they'd know some of these cases were fatalities. So ... it IS lethal force.

The suit also slams the City for poor training and discipline. As you know, Derek Chauvin had 17 citizen complaints, yet there's no evidence the Internal Affairs Dept. of the P.D. ever connected the dots as they investigated all of them.

And, one more thing ... the suit claims that probationary officers like Thomas Lane and J. Alexander Kueng were NOT allowed to question their supervisor. That works against the City, but it's the argument the 2 rookie cops are making in the criminal case.

The civil lawsuit does not specify the amount of damages the family is seeking.

Chauvin, who is still in jail, has been charged with 2nd-degree murder and 2nd-degree manslaughter.