It follows recent Kremlin targeting of civilian infrastructure.

American officials have called that a war crime, and it's just part of a panoply of acts that are now being investigated with the idea of prosecuting those responsible.

There's been a lot of discussion around war crimes in particular and some around crimes against humanity and even genocide.

And then, now, more recently discussion around aggression, which is the other international crime, and there are different ways different for prosecution.

There's been a lot of attention on the International Criminal Court, which is investigating war crimes and crimes against humanity.

And now, more recently, attention paid to a possibility of creating a special tribunal to prosecute aggression.

While Russia stands accused of far more acts that violate the rules of war, it is evident that the Ukrainians have also committed some that require investigation.

At least 10 Russians filmed surrendering last month were subsequently revealed to have been killed once defenseless, prompting an investigation, not least because westerners there helping Ukrainian prosecutors insisted upon it.

I expect that investigation to be a serious one and I'd also add this, that I do get the sense first and foremost that some very strict instructions have been given to Ukrainian soldiers about not committing crimes.

I think in large part because I think Ukraine wants to keep the support of the international community and do not want to be seen to be on a par with the Russian military and the Kremlin.

Following the crimes soon after the investigation in Bucha and other parts of northern Ukraine, some junior Russian soldiers were put on trial for murder and other crimes.

Inevitably, these early cases left many matters unsolved, like how those higher up the chain of command could be prosecuted

Last week, Olena Zelenska, wife of the Ukrainian leader, came to Westminster to open an exhibition cataloging the human cost of the war and to lobby for precisely that, an international tribunal able to charge those in the Kremlin with plotting and Aggressive war.

I would like to address you, Britain, and you ladies and gentlemen, with a request, we need to unite the world community, just as in 1942, to support a special tribunal against the aggression of Russia in Ukraine.

The war crimes issue presents politicians with a tricky dilemma.

Many want to support President Zelensky and, indeed, his wife and feel that being accused of war crimes is no more than Vladimir Putin deserves.

On the other hand, that might make a peace agreement even harder to achieve, prolong the conflict and so cost many lives.

I think what we're likely to see is that the I.C.C. Itself will bring charges against Putin within the next six months or so.

So that problem is also going to arise at the I.C.C.

And I guess what I would say is, well, what we're supposed to on the basis of a speculative possibility that it's going to continue the conflict.

We cannot proceed with any justice efforts.

I'm not sure that's palatable, or in any way, a practical way forward or else every dictator, every authoritarian, every perpetrator of crimes will benefit from that presumption that we shouldn't end out them that we shouldn't take action because they may continue doing what they're doing.

There are obstacles though.

Although the Security Council's permanent members, including the US, UK and France, are reluctant to back an international tribunal leveling charges against Russian leaders,

and the poor chances of getting them in the dock would suggest in absentia trials which involved their own issues.

Certainly, at the I.C.C., there wouldn't be absentee trials because they're ruled out in the statute.

I think in the Ukrainian domestic jurisdiction there is potential to have trials in absentia.

So that could be a possibility in terms of optics, I think, and the way it's perceived and the impact it could potentially have.

On the one hand, it allows for some sort of record and testimony to be given.

But on the other hand, if it's been ruled out of the I.C.C. and trials in absentia generally seem to be unfair to the accused.

It doesn't look terribly good to to go down that route.

In a recently liberated corner of Kherson district, war crimes investigators today exhumed a man believed to have been murdered by the Russians.

So many individual tragedies, and for now no clear idea how those responsible may be brought to account.