McKinney was born in Monticello, Florida, on November 3, 1950. He is one of six siblings, all of whom served in the United States Army. One served as an officer; one retired as a Master Sergeant; another served in the Vietnam War; and an identical twin, James C. McKinney, was a Command Sergeant Major.
In the fall of 1996, allegations of sexual misconduct by training cadre at Aberdeen Proving Ground and several other United States Army postings surfaced, and the Army instituted a substantial investigation with a toll-free telephone hotline that received nearly 60,000 calls within a matter of weeks. The task force established by Secretary of the Army, Togo D. West, Jr., to advise him about the situation included McKinney as the spokesman of the Army enlisted soldiers. In February 1997, McKinney was himself accused by a female former subordinate of improper advances. The Army suspended him from his duties that month while the charges were investigated; in May–October of that year, two Command Sergeants Major one being McKinney's twin brother, James C. McKinney; the other Jerry T. Alley—took over his duties in rotation. While McKinney was suspended from his duties as Sergeant Major of the Army, five more female soldiers accused him of similar improprieties. In November 1997, the Article 32 investigating panel completed its investigation and recommended charges for a court-martial. McKinney was thereupon permanently reassigned out of his billet and laterally redesignated to the rank of Command Sergeant Major; his successor, Robert E. Hall, was promptly installed. McKinney was acquitted of all sexual harassment charges, but was convicted of obstruction of justice and received a reduction in grade to Master Sergeant and a reprimand. Though he retired as a Master Sergeant, his retirement pay was calculated using the pay rate he earned during his tenure as Sergeant Major of the Army, in accordance with 10 USC § 1406. That law was subsequently amended by 10 USC § 1406 to prevent a recurrence.
Felony vehicular charge
On October 25, 2010, McKinney allegedly hit a man with his car on purpose, and was charged with felony malicious wounding. This occurred after McKinney was driving erratically with two slug passengers. When the passengers exited the car, one of them attempted to take a photograph of McKinney's license plate, and claimed that McKinney drove his car into him. Based on the preliminary hearing in April 2011, a judge ruled that the evidence in the case was sufficient to proceed to trial. McKinney was indicted for malicious wounding and reckless driving. McKinney submitted an Alford plea, which the court accepted. As a part of his plea agreement the felony charge was reduced to disorderly conduct. He was also sentenced to twelve months of incarceration, of which the judge suspended all but 10 days. McKinney was given credit for time served and only had to serve an additional two days.