Future risk:
You walk into a bar, in the corner there is a couple, clearly working class, he has work boots on, and she has a leopard print hoodie, eeesh, you don't like the look of them. You find out that the girl is 26, at 14 years old she ran away from home a few times, and self harmed up until she was 17. Clearly she had a bad relationship with her Mum, and she is unstable right? Look at her partner, 27 years old, grew up with a single Mum, smokes joint from age 15 to 23, was arrested for criminal damage twice, and common assault twice. But aged 19, he was offered a mechanics course, so he went on that and tried to turn things around, he reduced the amount of dope he smoked, but didn't give up completely. I'm sure if you got the woman to see a psych, that if you do that twice and get a good report, that if you put her in with a lesser qualified psych, who you offer a nice bounty to, that she could well be diagnosed with BPD, which would make her dangerous right. As for the lad, he might relapse into violence?
You take a deep breath, walk outside, and call the police. 'What's the emergency', you reply ' you have to help me, there is a risk that in the future I will be emotionally harmed', and explain the parents past. The emergency services operates has a unit dispatched to you immediately, and has the couple sentenced to 18 years imprisonment (the same amount of time people lose with their children) but actually, it's decided that they will be IPP, so they have an undetermined sentence (might not even finish at 18 years).
Now, if you cannot see why THAT would be wrong, then you are the sort of person I call a vulture.
As for historical evidence, a woman I counselled (had she not have shown me the paperwork, I would not have believed her) was said to be a risk of unstable relationships because of an incident of DV between her parents in Oct 83. Which is an interesting accusation because she was only born in April 83. Now THAT is the sort of evidence being used against parents who are fighting 'future risk' accusations.
I would like to add, and I am thinking about my 'foster cousins' as I write this. I whole heatedly wish every adopter who took on a child that NEEDED a loving home the absolute best, I truly hope that the natural parents back the eff off and leave you to do what they couldn't/wouldn't because that would be the right thing for them to do. However, for those who are happy that a child is made available at any cost, because they aren't the ones paying out. I don't need to wish you any misery, that will come when the child learns why it was adopted.