, ▁but ▁she ▁couldn ' t ▁w ake ▁him ▁up . ▁No ▁one ▁would ▁tell ▁me ▁why ." ▁Con sequently , ▁as ▁a ▁young ▁child , ▁Gr iss om ▁" play ed ▁doctor " ▁by ▁performing ▁ne cro ps ies ▁on ▁small , ▁dece ased ▁animals ▁in ▁the ▁local ▁area . ▁ ▁Gil ' s ▁mother , ▁Betty , ▁who ▁became ▁de af ▁as ▁a ▁result ▁of ▁the ▁gen etic ▁dis order ▁ot os cl eros is , ▁was ▁responsible ▁for ▁his ▁love ▁of ▁books . ▁As ▁a ▁result ▁of ▁his ▁mother ' s ▁de af ness , ▁Gil ▁became ▁fl uent ▁in ▁American ▁Sign ▁Language ▁in ▁order ▁to ▁be ▁able ▁to ▁communicate ▁with ▁her . ▁ ▁In ▁the ▁earlier ▁seasons ▁of ▁C SI , ▁it ▁becomes ▁clear ▁that ▁Gil ▁is ▁also ▁beginning ▁to ▁lose ▁his ▁hearing ▁as ▁well ; ▁eventually ▁he ▁requires ▁surg ery ▁to ▁fully ▁restore ▁his ▁hearing . ▁ ▁Gr iss om ▁earned ▁his ▁Bach elor ▁of ▁Science ▁degree ▁in ▁bi ology ▁mag na ▁cum ▁la ude ▁from ▁the ▁University ▁of ▁California , ▁Los ▁Angeles ▁( U CLA ), ▁and ▁his ▁Ph . D . ▁in ▁Bi ology ▁from ▁the ▁University ▁of ▁Chicago . ▁He ▁became ▁a ▁for ens ic ▁ent om ologist . ▁In ▁the ▁episode ▁" Gr iss om ▁vs . ▁the ▁Vol cano ," ▁Catherine ▁tells ▁the ▁story ▁of ▁losing ▁at ▁a ▁science ▁competition ▁as ▁a ▁child ▁against ▁a ▁" k id ▁with ▁some ▁l ame ▁red ▁an ts ." ▁Later ▁in ▁the ▁episode ▁Nick ▁also ▁reve