If it were not for me ,you would be in custody.这句话是对的.因为这是表示与现在相反的状态
意思是 有我你就不会被抓
If it had not been for me,you would have been in custody.这句话是与过去情况相反的状态,与现在没关系.
If it had not been for me,you would be in custody.这是错综虚拟语气,从句与过去相反,主句与现在相反.本句语法也对 ,但意思与原句不一样.
当初如果不是我,你现在就吃牢饭了.