A little google search found this neat link, the American Bar Association's list of the 12 Greatest Legal Plays:
http://www.abajournal.com/gallery/12_greatest_legal_pl Of them, only OEDIPUS THE KING and THE MAN IN THE GLASS BOOTH haven't been mentioned here, but still a neat and authoritative ranking.
And off the top of my head, some more plays, mostly that deal with crime, though some also courts:
ACCIDENTAL DEATH OF AN ANARCHIST (farce!)
AMERICAN BUFFALO
BLACKBIRD (though it's a question of statute of limitations here, it's certainly the after-effects)
ELMINA'S KITCHEN
FUENTEOVEJUNA (thank you, Theatre Lit classes in college)
LOOT (farce!)
MAURITIUS (though not necessarily a crime-and-punishment story, more a would-I-if-it-comes-to-it?)
MURMURING JUDGES
SAINT JOAN
THE ROMANS IN BRITAIN
THE VIRTUOUS BURGLAR (farce! Man, Dario Fo is fun.)
THE VISIT
Words don't deserve that kind of malarkey. They're innocent, neutral, precise, standing for this, describing that, meaning the other, so if you look after them you can build bridges across incomprehension and chaos. But when they get their corners knocked off, they're no good anymore…I don't think writers are sacred, but words are. They deserve respect. If you get the right ones in the right order, you can nudge the world a little.