If he is indigent, he can apply to the appellate court for assignment of appellate counsel. As for the new witnesses, you will need to show that this evidence could not have been produced at the trial with the use of due dilligence.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 577-9797 or via email at Eric@RothsteinLawNY.com. I was named to the Super Lawyers list as one of the top attorneys in New York for 2012. No more than 5 percent of the lawyers in the state are selected by Super Lawyers. The above answer is for informational purposes only and not meant as legal advice.
He has the absolute right to free counsel, either through the public defender's office in the county of conviction, or through the Assigned Counsel Program. You can apply by filing a "poor person" motion with the appropriate appellate division.
If this happened in Westchester County call the Legal Aid Society of Westchester County. He will only be assigned an attorney if he is under the income threshold. If he had an assigned attorney they should assign him one for an appeal. He should also ask his trial lawyer to help. If he cannot get an assigned counsel no private attorney will do it for free.