I would argue that this title is appropriate because the whole story centers around the strategy that the defense has for getting away with the crime.

At first, the story is pretty straight forward.  A crime has been committed and the criminal caught.  This is not very interesting.  But then we see what the case for the defense is.  It is very unusual and interesting.  So the story is named after its most interesting aspect.

I would also argue that this title is an ironic comment.  Usually, the phrase suggests a moral case -- an argument for why the defendant is not guilty.  Here, it is used much more cynically -- it is simply a ploy to literally get away with murder.