Can I appeal the decision of the Discharge Review Board?

Yes. Appeals are generally submitted to the Board for Correction of Military Records, but can also be filed in Federal Court. In addition, you can ask the Discharge Review Board to reconsider its decision based on “newly discovered evidence.” Army Regulation (AR) 15-80, at http://www.apd.army.mil/pdffiles/r15_180.pdf, contains all of the information you need to know about the process.