When and how to use the information you have in the matter is really a difficult thing to determine in this type of forum.  You can not just present it before sentencing.  You would probably need to make post trial motions, which are made many times to preserve your rights on appeal.  If you believe that the statements being made were not hearsay - and hearsay can be a tricky thing to determine - then you should speak with someone in your area who does criminal work and criminal appeal work on a regular basis to determine your next step.  You are going to challenge the judge's determination at trial as reversible error I assume but be aware that Judges are given great discretion unless there is a glaring mistake.  Good luck.