Assuming the DA needs the accuser to make out a case (and the DA doesn't alwyers) your lawyer will have the right to cross-examine the person during the trial.
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.
There are certain situations where the DA may be able to prove its case without the accuser testifying. One example would be if there were other witnesses to the crime.
Best of luck to you.