TL;DR: Basically a bonus case that explores the Sibyl system and supporting characters (namely Ginoza and Mika) a bit more, but breaks little new ground for world-building or the plot overall. 6.5/10
At 60 minutes, "Psycho-Pass Sinners of the System Case 1: Crime and Punishment" is less of a movie and more of a 3-episode bonus arc to Season 2 of Psycho-Pass. Our main focuses are Mika and Ginoza this time around, and fans of Ginoza/Mika can rejoice - they both get plenty of badass scenes, and Gino especially gets a beautiful fight scene towards the end.
Make no mistake, however - this is Season 2-level writing,
not Season 1-level. In other words, serviceable but nothing groundbreaking. Villains are pretty bland (though decently designed visual-wise), serving just as plot devices so the writers can make a point about society under the Sibyl System. The case is solved rather conveniently and neatly, and kind of predictably in all honesty.
The high points are definitely the characters and the fight scene at the end. Mika finally feels like an actual Inspector with enough redeeming qualities to stand on her own. Ginoza's screen-time allows him to showcase further growth in his character since Season 1, and reveal his thoughts on the other characters. The fight scene at the conclusion of the climax gets deserved full praise from me.
I was massively disappointed, however, that instead of getting new opening and closing songs after all these years, they simply remixed the OPs/EDs from Season 1/2. Remixes that somehow sound worse than the originals. So, a complete let-down on the music side of things.
Overall, I enjoyed the movie and was glad to be back with the characters I fell in love with in Season 1, and kind of liked in Season 2. Definitely don't hype yourself up for the story though. And if you have to pay to see it (like I did in theaters), it may not be worth the price of admission unless you're a die-hard Psycho-Pass fan.