It's disturbing to me that you're so focused on adultery, which isn't a crime in most places and is a personal matter for the couple involved. More than 70% of people cheat on a significant other at some point, so you'd be casting a wide net.
Why not instead look at real crimes like pay-for-play, fraud, sexual assault, etc.?
Everyone seems to be missing the point completely. I am not talking about building an adultery detector. I am talking about an object lesson. I am talking about showing Congress that the systems they are building in order to profile, label, and categorize the public based upon spurious statistical models are dangerous. Congresspeople are myopic, selfish creatures. If it doesn't affect them personally, they see it solely as a matter of "is it more power for us? Then the vote is yes!"
Adultery was picked because it is a very common behavior which is nonetheless viewed very poorly by society. It's the kind of thing which historically gets politicians into trouble. Being named as an adulterer is a realistic thing for a politician to fear, as it could ruin their life - the way getting labelled a terrorist or a pedophile or similar will be a reasonable thing for a citizen to fear when systems are debuted that use the same technology to label people with a likelihood score. That is why adultery was picked. If you wanted to do by pay-for-play where would you get your training data set? Where are the people who have actually lost their office because of that? The others are the same. We have a long history of politicians getting busted for adultery, so we can have a good training dataset. And the results will be garbage and useless. That's the whole and entire point. Once you have an automated system built, it doesn't matter whether its conclusions have any merit. It will hand out judgements, no one will be able to explain what basis they actually have, but investigations will be targetted and reputations will be destroyed.
My intent isn't even to accomplish any of that reputation destruction, it is simply to show Congress the ill use such systems can and will be put to.
Even if only to prove your point correct with 1 or 2 examples, this would be a great system to create! Let congress feel the pain that so many citizens unfairly feel.
There's a non-moralistic reason to be concerned with adultery in the case of politicians and public servants, which is that knowledge of it can be used for extortion.
Well, there's two sides to that. The other being they may be using their position of power to strong arm less powerful people into an affair, then discrediting their lover to cover their ass. Even if you don't care about that person being mistreated, it tells you something about their general priorities and how likely they are to be generally corrupt.
That's only because its a crime striking those laws down and removing them from the military system - would reduce the attack surface for bad actors trying to suborn people in to betraying the USA.
Likewise having a spiff 18 months ago at burning man or glasto isn't really a huge risk to security if its not a crime - would also help with recruitment for TLA's
They wouldn't care if you are gay. But if you are closeted and gay, that becomes something you can be blackmailed over and you will fail to get a security clearance. I don't know what they do when someone who can't get a clearance is elected... but the only reason they ask about lifestyle factors in background investigations is to determine if you're able to be blackmailed. If you're open, then obviously you can't be blackmailed with the fact you're gay or polyamorous or in an open marriage or whatever. It's the secrecy that's the problem. (This is all off-topic though, since I don't actually care about adultery and I don't think the system I'd build could legitimately catch anyone for adultery. It would do nothing but show that peoples reputations can be so easily smeared with basically no evidence using these sorts of systems. That's the point.)
Why not instead look at real crimes like pay-for-play, fraud, sexual assault, etc.?