Note that we use this idiom in informal speech.
Meaning
We usually use the idiom 'get away with murder' to complain or point out that somebody can do things that others are not allowed to do. In other words, someone does whatever they like without punishment or control.
Examples 👇
Can you get away with murder in Yellowstone Zone of Death? When considering a missing person case, Yellowstone National Park is intriguing for many reasons. CBS News
“When will they open a Cold Case on the Psycho Joe Scarborough matter in Florida. Did he get away with murder?" New York Post
Did Snoop Dogg really get away with murder? Snoop Dogg's an iconic figure, not only in rap but in the pop culture of the last twenty years. Film Daily
President Donald Trump questioned Tuesday morning whether "psycho" MSNBC anchor Joe Scarborough managed to "get away with murder" ... wflx
Making a killing: what can novels teach us about getting away with murder? The Guardian