GEOFF BENNETT: Russia took another step in its crackdown against dissent today.

In a Moscow courtroom, the noted opposition figure Vladimir Kara-Murza was sentenced to 25 years in prison for denouncing Vladimir Putin's war in Ukraine.

As Stephanie Sy tells us, Kara-Murza joins hundreds of other Russian opposition leaders and activists now behind bars.

STEPHANIE SY: Vladimir Kara-Murza was convicted of treason.

He received one of the harshest sentences for a political dissident since President Putin came to power.

He was arrested in Moscow last April after delivering a speech to the Arizona House of Representatives, where he called the Putin regime's actions in Ukraine war crimes.

As one of Putin's fiercest domestic critics, he was a key figure in the adoption by the U.S. Congress of the Global Magnitsky Act, which targets human rights abusers in Russia and around the world.

Before his arrest, he survived two assassination attempts.

For more in his sentence and the price of speaking up in Russia today, we turn to Alina Polyakova, president and CEO at the Center for European Policy Analysis.

Alina, thank you so much for joining the "NewsHour," as always.

The judge himself was under Magnitsky sanctions for human rights violations.

It was a closed-door trial.

Put this sentence into context for us.

ALINA POLYAKOVA, Director, Center for European Policy Analysis: Well, of course, Vladimir, whom I have known for many years, is an incredibly courageous person.

He went back to Russia.

He is a British citizen and a legal U.S. resident.

His family is here in the United States.

He went back to Russia to fight for his country, to fight for a Russia that could be free.

And this sentence passed down by a sham court, this was not a trial.

This was a sentencing event.

He was charged with high treason.

For what?

For basically calling what the Putin government is doing for what it is, which is a brutal war in Ukraine.

And it's very, very likely that, after the sentence, he will be transferred to a very, very harsh penal colony.

This is the highest so-called crime that the Russian government could charge him.

And the judge, of course, being sanctioned himself for human rights violations under the Global Magnitsky Act, cannot be called an impartial judge in this case, by any stretch of the word.

STEPHANIE SY: His wife, Evgenia Kara-Murza, reacted at an event hosted by The Washington Post today.

She said -- quote -- "This sentence is the high recognition of the effectiveness of Vladimir's work.

This sentence shows that they're so afraid of him."

Does Kara-Murza's conviction neutralize the opposition to Putin?

Or did he have enough impact on his fellow Russians?

Was he effective that the fight for human rights and democracy can continue without him?

ALINA POLYAKOVA: You know, Vladimir himself has said multiple times that he feels that his only failure -- and I'm paraphrasing here -- has been to not convince enough of his Russian citizen colleagues, friends, the people of Russia that the regime that they're currently living under is one that cannot be sustained and it's a repressive regime.

Of course, it's really difficult to see a positive path forward here.

Like other political prisoners in Russia, Vladimir Kara-Murza faces a very bleak reality now; 25 years is truly a life sentence for him.

But he remains, I think, incredibly courageous in the face of what many would be really beaten and defeated by.

And, of course, Evgenia, his wife, who you just quoted, has been crusading on his behalf and advocating both the British government -- of course, again, he's a better citizen -- and the United States, where he has been residing with his family, to really raise greater condemnation, to push back on the Russian government's sentencing, to do whatever we can to elevate his case to a global stage.

STEPHANIE SY: Tell us what you know about Vladimir's health.

He had been previously diagnosed with something called polyneuropathy, Which I understand affects the nerves, and which his lawyer has linked to previous poisoning attempts.

What is his current condition?

And is he getting medical care?

ALINA POLYAKOVA: Well, of course, visits by his legal counsel, as well as by independent medical professionals, has not really been happening, to say the least.

What's clear is that Vladimir is very, very ill.

He does have a serious neurological condition that has been the result of a previous poisoning by the Russian government in 2017.

And that requires a lot of medical care, requires a lot of physical therapy.

After that poisoning, he walked with a cane for a very long time.

And it's our understanding now, based on the information we're able to get, is that that condition has worsened very, very rapidly and significantly, to the point where he has trouble walking.

He's having trouble using one of his arms.

In fact, even this sham trial had to be postponed from March because he wasn't able to go into the courtroom.

So what we really need now is for him to at least be able to see an independent doctor who might be able to help him to receive access to medical care.

This condition, to be clear, in the conditions that Vladimir is currently living in, will likely be fatal.

So this truly is a life sentence for him that he's very unlikely to survive if this continues.

STEPHANIE SY: And, Alina, quickly, we just reported a few days years ago that another popular opposition leader, Alexey Navalny, who is serving an 11-year sentence in a penal colony, is suspected of having been poisoned again.

What does it tell you about Putin's state of mind and political calculus now that two of Russia's most powerful opposition leaders are imprisoned?

ALINA POLYAKOVA: Well, very similar to Alexey Navalny, the sentencing of Vladimir Kara-Murza, it's -- there's no execution day, but this is a slow death that they're both being sentenced to.

And the -- what I think that tells us about the state of the Russian society is that people are gripped by a deep fear, because both of these individuals have name recognition in Russia.

They're known people, maybe not to all Russians, because the Russian information is so controlled by the government.

But they certainly have been prominent political activists, journalists in their own right.

And the Kremlin is very much trying to make an example of them.

The Russian government has also done this to just average Russian citizens who dare to speak out against the Kremlin's own lies about what is happening in Ukraine.

And it's quite concerning, but I think what we're seeing in Russia is really the emergence of a North Korea-like government.

STEPHANIE SY: Alina Polyakova with the Center for European policy Analysis, thank you so much for sharing these insights about your friend.

ALINA POLYAKOVA: Thank you.