Wisconsin Statutes Police Regulations (Ch. 163 to 177) § 165.79. Evidence privileged

(1) Evidence, information and analyses of evidence obtained from law enforcement officers by the laboratories is privileged and not available to persons other than law enforcement officers nor is the defendant entitled to an inspection of information and evidence submitted to the laboratories by the state or of a laboratory's findings, or to examine laboratory personnel as witnesses concerning the same, prior to trial, except to the extent that the same is used by the state at a preliminary hearing and except as provided in s. 971.23. Upon request of a defendant in a felony action, approved by the presiding judge, the laboratories shall conduct analyses of evidence on behalf of the defendant. No prosecuting officer is entitled to an inspection of information and evidence submitted to the laboratories by the defendant, or of a laboratory's findings, or to examine laboratory personnel as witnesses concerning the same, prior to trial, except to the extent that the same is used by the accused at a preliminary hearing and except as provided in s. 971.23. Employees who made examinations or analyses of evidence shall attend the criminal trial as witnesses, without subpoena, upon reasonable written notice from either party requesting the attendance.

(2) Upon the termination or cessation of the criminal proceedings, the privilege of the findings obtained by a laboratory may be waived in writing by the department and the prosecutor involved in the proceedings. The employees may then be subpoenaed in civil actions in regard to any information and analysis of evidence previously obtained in the criminal investigation, but the laboratories shall not engage in any investigation requested solely for the preparation for trial of a civil matter. Upon appearance as a witness or receipt of a subpoena or notice to prepare for trial in a civil action, or appearance either with or without subpoena, the laboratories shall be compensated by the party at whose request the appearance or preparation was made in a reasonable amount to be determined by the trial judge, which fee shall be paid into the state treasury. In fixing the compensation the court may give consideration to the time spent in obtaining and analyzing the evidence for the purposes of criminal proceedings.