There are a couple of problems with a personal injury suit on your son's behalf.  First, in order to have any kind of case against the police, you would need to show that your son's condition is (significantly) worse because of the delay in receiving medical treatment.  If you cannot find a doctor who says that your son suffered ADDITIONAL injury as a result of a refusal to allow him to see a doctor, then your son will not have damages to justify a case against the police.  Moreover, any personal injury action on your son's behalf is complicated by the fact that he was drunk and arrested for DUI, and therefore 1) probably at fault, and 2) an unsympathetic plaintiff.  Nevertheless, it doesnt hurt to consult with a personal injury attorney to evaluate the merits of any potential claim in greater detail.