He'd given this man, a stranger, the benefit of the doubt. He'd presumed he was innocent; the kind of mistake a novice might make. (2.5.1)
In Soviet Russia, innocence presumes you. This is actually pretty crazy, when you think about it: all you have to do is be questioned about a crime to be considered a chief suspect. If you were so innocent, then why did you get involved in the first place, huh? Huh? You weren't involved, you say? Then why are you being questioned?
The judicial system could be bypassed entirely. Leo had heard of prisoners who lay abandoned for weeks and doctors who served no other purpose than the study of pain. (2.7.3)
Yikes. This place seems more like a medieval torture chamber than a modern prison, with every aspect of the facility designed to inflict as much pain as possible. Here's the crazier part: most of the people being tortured are innocent of their crimes. It's a lot easier to arrest an innocent man than to search for a guilty one, after all.
"You took justice into your own hands. That is not acceptable. That is never acceptable." (2.7.32)
This is the point in every cop movie when the chief makes the hero turn in his badge and gun. Jokes aside, this exchange shows that for the MGB, following orders is more important than finding the truth.
It was inevitable that Babinich was going to be found guilty and inevitable that he was going to die. The system didn't allow for deviation or admissions of fallibility. (3.21.9)
Leo has seen enough trials to know how this one will end. If someone goes to court, then they're guilty—no exceptions. To do otherwise would be considered a grave affront to the Soviet political system, as it implies that the government is not as infallible as it claims. And if you keep making grave affronts, well, you might end up at your own trial.
Quite by chance he'd found a second undesirable: a suspect he could call murderer without upsetting the social theory. (3.26.2)
General Nesterov is better than most, but even he fails to achieve real justice. Crimes can be blamed on mentally ill kids or gay men—easy scapegoats whose communities have already been forced to the bottom rungs of society. It's sad, but this is all too common in real life, too.
In the pursuit of justice he'd unleashed terror. In the pursuit of a killer, one hundred and fifty men would lose their lives. (3.26.12)
Well, that didn't turn out as planned. For the first time in his life, Leo is actually fighting for justice—it's a cruel irony that this noble quest leads to something so heartbreaking. We're sure that Leo feels the emotional weight of it, too.
He felt [...] part of a horrific, absurd charade, a player in a grotesque farce—the naive dreamer, striving for justice but leaving a trail of destruction in his wake. (3.30.10)
Alex's death crushes Leo. While Leo is pained by what happened to all of the men, Alex's suicide hits the hardest because the two of them were friendly with each other; in fact, Alex had even given him a few clues about the killer. All of a sudden, Leo's idealistic quest seems to be spinning out of control.
"And together you plan to solve this crime?"
"If the state won't then the people will have to." (4.36.52-54)
Leo has learned that real justice doesn't come from the government; it comes from a united community working towards a single goal. What's more, Leo would never have been able to stop the killer without these people's help.
While guards were indifferent to whether prisoners lived or died, escape was unpardonable. It made a mockery not only of the guards but of the entire system. (4.50.12)
As usual, doing the right thing is only secondary to protecting the State's image. On some level, these guys must know that guilt and innocence are completely arbitrary—all that matters is ensuring that they don't end up as passengers on one of these trains. It's not a pleasant world these folks live in.
If Leo and Raisa failed for whatever reason, if the murders continued, then the family would inherit the investigation [...] He mustn't be allowed to survive. (4.55.31)
By bringing regular folks into their investigation, Leo and Raisa ensure that their work will not be in vain. Should anything bad happen to them (spoiler alert: it doesn't), they can be content in the knowledge that others will pick up where they left off. Now that's some juicy justice.