If you commit a crime in unclaimed territory, where do you get tried?

They would be tried in the country they came from (the one that sent them to space) or in the country that owns the ship they were on (like if someone killed someone in a chinese spacecraft they could be tried in china because they technically were in chinese property).
This is just speculation but it is probably what would happen because there is no precedent for a case like this.

The suspects would be tried under Klingon Law and entitled to a trial by combat

Crimes can be tried in the country where: (1) the act was committed or planned, (2) the victim was, (3) the victim is a citizen, national, or resident, (4) the perpetrator was, (5) the perpetrator is a citizen, national, or resident, (6) that owns the ship, airplane, or spaceship where the act was committed, (7) the ship (etc) took off from, (8) the ship (etc.) landed, (9) that owns, or their companies own, the stuff (phones, computers, internet connections, etc.) used in the crime, (10) the country designated by treaty.

There are probably other reasons for where you could be tried. In the case of LtCol Anne McClain, she is a US citizen, and the victim is a US citizen, and the bank involved is in the US. The equipment used was owned by US and Russian space agencies, but Russia has shown no interest in prosecuting. McClain's lawyer's aren't even going to bother bringing up the "problem" of if the US has authority to prosecute -- it's just too obvious that they (the feds) have the authority.

The bank wasn't in space, so the hacker would be subject to the laws where the bank existed. The lunar killer would be subject to the laws of the nation that the spacecraft flies under, exactly the way it works on the high seas of international waters … assuming he/she can be apprehended.

It's not the issue WHERE the crime was committed, but what country the law was broken in & where the criminal suspect goes.

In this case, the ISS is considered international territory (similar to "international open waters")... HOWEVER, the crime occurred on servers residing in the US, so federal law applies, & the astronaut in question being a citizen of the US. While the astronaut can't officially be charged with the crime, but will be charged upon landing in the US.

The same would currently hold true on the moon. As there's no governing body on the moon & it's considered an internationally neutral territory by several nations with two treaties (The Outer Space Treaty of 1967 which restricts exploration & development of the Moon for peaceful means, banning the installation of military bases & weapons of mass destruction on the Moon; AND the Moon Agreement of 1979, which prevents the exploitation of the Moon resource by any single nation). Therefore, if somebody did commit murder (or manslaughter) on the moon, the governing body of the group would address on the moon OR send the criminal back to Earth to be tried by the country of the victim.

To put things into more plausible context would be an international flight. In this case, while the crime occurs in international territory, the legal ramification would occur upon the plane's landing. The law in the landing country would apply to the crime that occurred.

Hope that clear things up.

Depends on which crater the crime was committed on.

Russias? Or USAs?

If there's evidence of the crime like a video, then he will be arrested immediately once he lands on Earth.

But if I was on that kind of situation, I just make sure that no cameras rolling during the crime, and just let his body floats to the endless space. Because nobody would spend literally millions of dollars to bring the police to the moon for investigation, or trying to collect the body in space. So they can only conclude that the victim was died to some accident.