From nowhere 4

should have..could have

From English drama "Sherlock" S03X03 After Sherlock's lie to get into Magnussun's private room had been exposed to Janine.. she said "You shouldn’t have lied to me. I know what kind of man you are. (but you did) 거짓말은 하지 말았어야지. We could’ve been friends. (but we are not anymore.) 친구는 될 수 있었을텐데.. should have+past participle is used to talk about past event which did not happen, or which may or may ..