1
general::
Escape the consequences or blame for, as in Bill often cheats on exams but usually gets away with it. [Late 1800s] 1. get away with murder. Escape the consequences of killing someone; also, do anything one wishes. For example, If the jury doesn't convict him, he'll have gotten away with murder, or He talks all day on the phone? 2. the supervisor is letting him get away with murder. [First half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): get away with something [and] get by with something
to do something and not get punished for it. (See also get away with murder.) • You can’t get away with that! • Larry got by with the lie., Phrase(s): get away with someone or something
to escape, taking someone or something with one. • The kidnapper got away with little Brian. • The burglars got away with a lot of cash and some diamonds.
McGrawhill's American Idioms And Phrasal Verbs