Surely if you read courtroom/crime thrillers/police procedurals written by novelists who aren't involved in the criminal justice system, you simply disengage the part of your brain that bothers about inaccuracies, though? Or you just don't read them.
I have a friend who is a forensic unit of the police, a friend who is a forensic archaeologist, and friends who do criminal law, and none of them ever read or watch that kind of thing, as the inaccuracies are far too bothersome to make it enjoyable (or to make it enjoyable for anyone watching TV with them while they scream about shoecovers or exhumation procedures. 
The problem with novelists in general (not genre fiction specifically) is that unless you stick to writing strictly of things you have yourself experienced (in ways that might be as restrictive as only writing characters who are your own generation, sex and nationality, doing things in settings you are very familiar with), you are up against the things you don't know you don't know, so you can't research them. Hence, as a very obvious example, all the vast amounts of Harry Potter fan fic in which Hogwarts has study halls, hall passes, nerds and jocks, and in which Hermione wears a jumper and pantyhose.
An editor isn't going to know these unknown unknowns, either, unless you are writing a character who happens to chime with either his/her own experience or have chosen for setting an area they happen to be expert in. Even historians of a specific period will often not know the kinds of things a novelist needs to know, and besides, the world is not full of experts in field x.criminal barristers/forensics specialists sitting about desperate to do free (or even paid for) reads for novelists.
I'm currently writing something that has an architect as a key character, and while I have researched, asked architects I know lots of questions, and will be asking an architect friend to skim a full draft for any egregious errors, I'm sure he will find some that I didn't avoid.