The Eighth Amend­ment pro­hibits cru­el and unusu­al pun­ish­ments. But prov­ing an Eighth Amend­ment vio­la­tion based on dan­ger­ous or unfit prison con­di­tions is dif­fi­cult because it requires a show­ing of sub­jec­tive cul­pa­bil­i­ty on the part of prison offi­cials. Fed­er­al courts have grown increas­ing­ly aware of the harm­ful nature of soli­tary con­fine­ment, par­tic­u­lar­ly for juve­niles, the men­tal­ly ill, and inmates with spe­cial med­ical needs. In this Con­tri­bu­tion, Jane M. Mahan (’22) argues that the place­ment of vul­ner­a­ble inmates in soli­tary con­fine­ment for a peri­od exceed­ing fif­teen con­sec­u­tive days should be per se uncon­sti­tu­tion­al under the Eighth Amendment.