AIBU to tell my cousin to throw her son out?

YANBU.

If she doesn't press charges then how would she feel if he does this to another woman and potentially causes even more harm?

She should press charges and change the locks on the house and notify the police he is not coming home.

The boy needs help and this is probably the only way he will get any.

Yes you were right in your advice OP.
If she drops the charges and allows him back into her home then goodness knows how his violence will escalate.

Well you can advise her
But its up to her wether she throws him out.

You can advise all you want but it is her decision.

it’s her life she needs to live it.

This albeit I would be saying WHEN rather than IF.

You did the right thing, but I hope you support her if she does drop the charges too. Poor woman.

It won't be up to her to drop charges. The police will decide if there is enough evidence to prosecute him. She can withdraw her statement but that may not be enough.

Your advice is right. But it is up to her if she takes it? Where is this lad’s dad? He clearly needs a strong hand. He should go and live with him ideally.

No, fuck that.
I don't think that you get the option to drop charges.
That charmer wouldn't spend another minute under my roof

The whole ' press charges' thing is American. The police will make the decision whether to prosecute.
There is no way she should be allowing him to come home. I completely agree with you. If he ends up on the street it will be the consequence of his actions.
Has he knocked her about before?

Yes I think you have the right advice.

Is it easy? No! A mother instinct in general is protect their children.

However if a DP/DH did this the advice would be to run for the hills so the advice needs to reflect head what’s safe for her and not what emotionally her heart will be saying.

Your poor cousin - her own child!

yanbu, she shouldn’t drop the charges.

You're right she shouldn't allow him to live with her after attacking her.

How much she supports him as opposed to cutting contact would depend on the other circumstances for me - was he a victim of or witness to ongoing violence from his father before his father left? Is he vulnerable in terms of learning disabilities or neurodivergence or mental illness?

Those things don't mean he should live with her now he's attacked her, but if he is vulnerable I'd try to get a roof over his head and services in place, though it's hard as he's an adult. I've worked with families who keep supporting adult children in circumstances like this, but always with learning disabilities and co-occurring conditions meaning the individual is very vulnerable and cannot look after themselves completely independently.

If he's not got objective vulnerabilities and is just nasty then obviously no support necessary, he's burnt his bridges with the physical attack, though it's very sad it got to that point.

And how would your friend feel if your cousin let him back in and got murdered?

You can offer someone the best advice in the world and there's no guarantee that they'll follow it.

I'm sure she can see that if she does proceed with not allowing him back in and having him face the consequences of his actions, the results will be unpleasant for her. And if she doesn't, there will be more unpleasantness to follow. She did the right thing but it will be a difficult road for her.

Ultimately, making him leave her house will be better for him in the long run rather than excusing his behaviour and allowing him back to continue the abuse. But it's debatable whether she has the strength to follow on.

That's true.

But its helpful when the victim cooperates with the police and makes a statement and allow photos of injuries to be used as evidence. That way the police can prosecute.

If a victim refuses to cooperate, retracts their statement etc... then prosecution often doesn't happen as there isn't sufficient evidence.

As a mother I know I could never do this to my own child.
there will be reasons why he is so angry, unmotivated and reckless.
his behaviour is inexcusable but putting him on the streets is unlikely to help anyone.

She can’t decide whether the police charge him or not. Because she reported it, it’s now solely in the crown prosecution services hands to make a charging decision. By the seriousness of her injuries I’d be shocked if they didn’t prosecute. What a vile man, he needs a good wake up call.

He will have access to emergency accommodation which will likely be a shared room with other men who may have substance use, criminal pasts, mental health issues… I mean.. you can understand her reluctance. I think you’re right in what you advised but it is easier said than done. Very few parents make rational decisions about their own children.

What’s the history here? He sounds very angry.

Then you're a fool
He's not a child anymore. He knows that beating up your mother is wrong.

No I’m not a fool

@Twoshoesnewshoes
You are wrong. He could kill her. Or kill another person.