While subduing Darren Burley in 2012, deputies used their knees to pin him to the ground. He died 10 days later.
Jurors found that Burley was 40% responsible for his own death, so an appeals court later reduced the payout by $3.2 million.
RELATED: Body camera footage captures distraught George Floyd: 'I'm not a bad guy'
The justices ruled Monday that the county owes his family the entire $8 million.
The county and sheriff's department has not yet commented.
The Associated Press contributed to this report.