Anne Sacoolas is somewhat more nuanced than that, mostly because Diplomatic Immunity is a strange necessity for functional alliances.
The underlying gist is that people important to the government or possessing sensitive knowledge are immune to prosecution from allies to prevent prosecution being a viable method of coercing information from government officials. Ie the US cannot charge a UK ambassador, because that ambassador may be tempted to leak secrets in exchange for leniency.
The same typically goes for family members for the same reason.
In this case Sacoolas had done undercover work for the CIA at some point, so likely had knowledge the State Department did not want leaked. Her husband was active in the CIA and likely also had similar knowledge.
The same is true in reverse. You can look up the court cases, the US has had to drop several cases due to diplomatic immunity.
There is an element of might makes right to diplomatic immunity because there is no real higher power to enforce it. If a country is willing to weather the political fallout (and reciprocal loss of diplomatic immunity), potential hostile action, and can get their hands on the perpetrator, they’re free to ignore diplomatic immunity.
In practice, diplomatic immunity is almost always respected, even when it could probably be ignored, because of onlookers. If the US ignores eg Kenya’s diplomatic immunity (who they can likely afford to piss off), it might worry the UK who the US does not want to piss off.
Diplomatic immunity is very, very rarely ignored, but is waived with some regularity. The US is particularly liberal with granting diplomatic immunity, though, and more reluctant to waive it than most countries.
There were a lot of questions about whether Sacoolas had actually had diplomatic immunity, due to not being a diplomat and not having the paperwork a normal diplomat would have. Although perhaps it's to be expected that spies' paperwork would be irregular. There was also a claim that Sacoolas had some sort of secret diplomatic immunity under a secret treaty. Some reports claimed US spies had diplomatic immunity only while on the military base, while their families had immunity even while off base, implying Sacoolas would have immunity unless she was a CIA employee. Which she was at the time, according to some reports. Or was she merely a former CIA employee? Understandably, the CIA is not in the business of confirming such matters.
I agree with you that there is nuance involved.
I would say the precise nuance is irrelevant. Whether Sacoolas had immunity in theory is unimportant - only that she had immunity in practice.
Sort of. My understanding is that the UK decided she did not have immunity, but the US disagreed and refused to extradite her.
Then she agreed to voluntarily appear (virtually) and plead guilty, but was given a suspended sentence because the judge noted there was no way to enforce any actual punishment.
So you’re right, though it played out basically the same way it would have if she was immune. The UK was never actually able to punish her, but they do technically get to say she was found guilty.
The underlying gist is that people important to the government or possessing sensitive knowledge are immune to prosecution from allies to prevent prosecution being a viable method of coercing information from government officials. Ie the US cannot charge a UK ambassador, because that ambassador may be tempted to leak secrets in exchange for leniency.
The same typically goes for family members for the same reason.
In this case Sacoolas had done undercover work for the CIA at some point, so likely had knowledge the State Department did not want leaked. Her husband was active in the CIA and likely also had similar knowledge.
The same is true in reverse. You can look up the court cases, the US has had to drop several cases due to diplomatic immunity.
There is an element of might makes right to diplomatic immunity because there is no real higher power to enforce it. If a country is willing to weather the political fallout (and reciprocal loss of diplomatic immunity), potential hostile action, and can get their hands on the perpetrator, they’re free to ignore diplomatic immunity.
In practice, diplomatic immunity is almost always respected, even when it could probably be ignored, because of onlookers. If the US ignores eg Kenya’s diplomatic immunity (who they can likely afford to piss off), it might worry the UK who the US does not want to piss off.
Diplomatic immunity is very, very rarely ignored, but is waived with some regularity. The US is particularly liberal with granting diplomatic immunity, though, and more reluctant to waive it than most countries.