. >> reporter: kevin henry and another former player, najeh davenport, are suing the nfl accusing themng paying head injury claims based on a formula that discriminates on the basis of race. the formula, they say, assumes black players start at a lower cognitive level than white players, making it harder for black former players to qualify for compensation. it's a controversial practice called race norming in which test results are adjusted to account for supposed differences between demographic groups. >> there's a assumption that people of different races, especially black people, that their bodies function differently. >> reporter: and while the nfl insists the formula is optional, an abc news investigation has found that some clinicians who evaluate former nfl players believe they are required to apply the formula. >> football doesn't give you an expiration date. it just happens. you just expire. i've had ten concussions or more and that's not even counting practice. >> reporter: after his time in the league kevin henry says he began suffering from depression, memory loss and bouts

. >> reporter: in the case of najeh davenport? , nfl, did you then appeal that decision in order to discriminate against them? >> reporter: with their lawsuit, henry and davenport are seeking damages and asking the court for a declaration that requiring race norming in the settlement would be illegal. >> i'm not an ignorant guy, i'm not stupid. so why are you judging me like that? when it comes to compensation on this concussion lawsuit, i'm looked at differently. and it pisses me off. so let's change the system, man. if you -- if we change the system, then everybody would be compensated. make it a fair system. >> reporter: the nfl has received around 3,000 claims for compensation from former players, and already paid out more than $800 million, about 1 in 3 claims are approved. but the nfl has repeatedly denied requests to release demographic data on program payouts, making it impossible to determine whether this formula has skewed awards because of race. >> we've asked the nfl, we've asked class counsel who represents the settlem

. >> reporter: kevin henry and rp najeh davenport, are suing the nfl, accusing them of "avoiding payingead-injury claims based on a formula that discriminates on the basis of race." the formula, they say, assumes black players start at a lower cognitive level than white players, making it harder for black former players to qualify for compensation. it's a controversial practice called "race norming," in which test results are adjusted to account for supposed differences between demographic groups. >> there's the assumption that people of different races, especially black people, that their bodies function differently. >> reporter: and while the nfl insists the formula is optional, an abc news investigation has found that some clinicians who evaluate former nfl players believe they are required to apply the formula. >> football doesn't give you an expiration date, it just happens. you just expire. i've had ten concussions or more and that's not even counting practice. >> reporter: after his time in the league, kevin henry says he began suffering from depression, memory loss and bouts of