Casey Royer (born October 8, 1960) is an American musician who began his career playing drums for SoCalpunk bands The Detours and Social Distortion at age 18 in 1978. He then moved on to play for The Adolescents off and on from 1980–87. After The Adolescents' first breakup in 1981, Casey went on to form his own band D.I., performing as a frontman for the first time. When The Adolescents regrouped in 1986, Casey returned to the band but would leave before the 1987 reunion album Brats in Battalions was recorded. He rejoined them again in 2001-2002 for their 20th Anniversary Tour. Casey also joined former Adolescents bandmates in ADZ from 1989–93, after which he again made D.I. his primary focus. He has been the only constant member through myriad D.I. lineup shifts since the band's inception.