Only the States Attorneys office can make the decision to drop or pursue charges. If you have received a "victim letter" and you do not wish to pursue charges, simply disregard the letter. If the case has already been charged, you must contact the prosecutor handling the case. It is that prosecutors decision on whether or not to pursue a charge. There may be serious consequences to you for your lack of cooperation. You should not assume that by ignoring correspondence or subpoenas a case will be dropped. Victims wanting to drop charges should fill out an Affidavit at the States Attorneys Office requesting that the States Attorney discontinue prosecution.
Please note: Filling out an Affidavit does not guarantee the State will not continue charging a case.