I was hoping for some more details here, but I'll provide you with an answer. If I don't touch upon what you want to hear, you can reply here with a follow up and I can add more information.
I am a New York State criminal lawyer. In my experience, the only reason that a defendant would be denied a public defender on a criminal case would be because he is financially ineligible. A defendant must be indigent -- at or below poverty level -- before he is entitled to a free lawyer. You can call the public defender's office and talk to them about this defendant. If they feel that the judge was in error and this young man qualifies for free representation, they can bring that argument to the judge and try to change his mind. If they can't, at least they would preserve that issue for an appeal down the road if the defendant loses his case.
The overwhelming majority of criminal lawyers who do pro bono work are public defenders, because there is a Consittutional right to an attorney for poor people charged with a crime and threatened with the loss of their liberty. There are some organizations that do criminal pro bono work, but not nearly as many as do civil law.
Here are some links to the pro bono agencies available in New York state. You may have to make a number of phone calls, but you should find some assistance, especially as lawyers in the pro bono loop usually know of others and you will be able to get other referrals as you go along.Here are some other links.
As brutality is involved and there are civil rights issues here, you can also contact the American Civil Liberties Union. The ACLU advocates for prisoner's fundamental rights and they have branches all over the country. If you contact the national organization, they should be able to link you to a local chapter and to pro bono lawyers in your area who can be of assistance.
Finally, a good and often overlooked resource available for free or low priced legal assistance is law school clinics where law students research, write and handle actual cases and issues under the supervision of a practicing professor/lawyer. Some of these law school clinics are very highly regarded, and if a court appearance is called for, the professor goes to court.
Law students are trained legal researchers. They are energetic, idealistic and enjoy putting their efforts into a cause they can believe in. New York State has an abundance of law schools. Here's a list of them. The kinds of clinics that they have are noted on the list. These clinics are either free to the public or have a sliding fee scale. They too would know of other available resources.Good luck!