Okay so here it is my friend is being charged with murder(shooting somebody) the accused has health problems such as heart problems & has had brain surgery not sure of the reason but I think he has some brain condition) anyway,when the police caught him to arrest him he didn't resist arrest nor have any weapons on him but the police/task force hit him in the head with one of those shield things,so what I'm wondering is,are they aloud to do that?even though he wasn't a threat to them?can anything be done about that due to his brain condition/surgery/heart problems?if so what?

If he is just standing there, giving up, no they can not "hit" him, but it does not stop the arrest, does not effect the trial, he can press charges against the police officer who did it.

But. This was considered a high risk, arrest, And someone who is being arrested for murder, will always be considered armed, until they are searched and no weapon is found. If he did not get on the ground fast enough, or perhaps they just forced him down. Forcing him to the ground would be acceptable in a high risk felony arrest.

Because of the charges against him, he was considered armed and dangerous.

Im relatiely certain the police didn't just walk up to him and hit him in the head. There is more to the story we aren't being told.

Your questions can't really be answered by anyone online. You don't even know any basic details about his medical background, much less how the arrest happened. He will have a defense lawyer, and it's that lawyer's job to gather all the facts that can help with his defense.

Charging the police with improper procedure will take a ton of time, evidence, and eye witnesses, and it will need to be shown that his medical conditions were worsened. It won't help with his murder case. It isn't anything like some of the recent cases in the news.

Notice how often these stories are told in the third person, but manage to sound like they are talking about themselves at the same time.

What is clear, they will have a lawyer working on their behalf with a crime of this nature.