MacKENZIE, J.

Plaintiff appeals by leave granted from an order denying in part his request for pretrial discovery of certain of defendant's records and documents. We affirm in part and reverse in part.

Plaintiff's decedent was struck on the head with a baseball bat during a robbery. Four Waterford Township police officers, including Officer J. Humbaugh, were summoned and discovered the decedent wandering and disoriented. Apparently believing that he was intoxicated, the officers did not take the decedent into protective custody or seek medical treatment for him, but instead returned him to his apartment, where he died. This action, brought pursuant to 42 U.S.C. § 1983, against the Waterford Township Police Department (hereafter defendant) and the four officers followed.

Shortly after the incident, defendant conducted an internal affairs investigation, and Officer Humbaugh was suspended. He filed a grievance which, within "a couple of months" of the incident, proceeded to arbitration and the taking of testimony of an unknown number of witnesses. The arbitration resulted in a determination in favor of the officer.

Plaintiff sought discovery of a number of documents, including the complete record of the Humbaugh arbitration; a complete copy of the internal affairs investigation, conclusions, and recommendations; and copies of those portions of the personnel files of the four officers involved in the incident, as well as all other officers in the department, dealing with their training or prior complaints of improper response to medical emergencies.

The trial court initially entered a protective order denying plaintiff's motion for production. Later, however, the court conducted an in camera examination of the internal affairs investigation file and the personnel files of the four officers involved in the incident. The court then ordered defendant to produce certain documents in the four officers' files relating to their training, as well as a rules-of-conduct document in the internal affairs investigation file. Plaintiff's requests for the remainder of the internal affairs investigation file and personnel files, along with his request for the Humbaugh arbitration record, were denied. That denial is the basis of this interlocutory appeal.

Michigan law is strongly committed to open and far-reaching discovery, and generally provides for discovery of any relevant, nonprivileged matter. See Eyde v Eyde, 172 Mich. App. 49, 54-55; 431 N.W.2d 459 (1988); MCR 2.302(B)(1). Privilege is governed by the common law, except where modified by statute or court rule. MRE 501.

The threshold question in this case is whether there is a qualified privilege which protects from disclosure documents reflecting a governmental agency's evaluative or deliberative processes. We find federal law on the question persuasive, and hold that such a privilege exists in Michigan.

The deliberative-process privilege is often traced to Kaiser Aluminum Chemical Corp v United States, 157 F. Supp. 939, 944-947 (Ct Cl, 1958). Citing both American and English precedent, Kaiser outlined a privilege for "confidential intraagency advisory opinions," based on a policy of protecting "open, frank discussion" concerning governmental action. Id., p 946. The privilege does not, however, extend to "objective facts" upon which decisions are based. Id. Although originallys applied to the federal government, the privilege has been applied by federal courts to discovery requests in litigation involving civil rights claims against state and local officials as well. See Wood v Breier, 54 FRD 7, 12 (ED Wis, 1972). State courts have also adopted the doctrine as a common-law privilege. See, e.g., Hamilton v Verdow, 287 Md. 544, 559-562; 414 A.2d 914 (1980).

Whether applied to administrative litigation against the federal government or civil rights litigation against police departments, the central question in the application of the privilege is whether the material sought is factual or evaluative. See McClelland v Andrus, 196 US App. DC 371, 379-381; 606 F.2d 1278 (1979); Wood, supra, p 12. The purpose of the deliberative-process privilege is to foster freedom of expression among governmental employees involved in decision making and policy formulation. Accordingly, factual material falls outside the scope of the privilege; to be protected, the material must comprise part of the deliberative or evaluative process. McClelland, supra, p 380. Moreover, the privilege protecting deliberative and evaluative data may be overcome by a sufficient showing of need. Liuzzo v United States, 508 F. Supp. 923, 938 (ED Mich, 1981); McClelland, supra, p 382.

Applying the deliberative-process privilege to this case, we find no abuse of discretion in the trial court's refusal to order further disclosure of defendant's internal affairs investigation file. It appears that plaintiff has already received all factual material from the file, including witness statements and the department's rules of conduct. The remainder of the file seems to consist of the evaluative findings of the investigators, which are subject to the privilege.

Plaintiff argues that the internal affairs findings and analysis are needed in order to establish the department's ratification of or acquiescence in the officers' conduct. City of Canton v Harris, 489 U.S. 378; 109 S Ct 1197; 103 L Ed 2d 412 (1989). However, such evaluative data falls squarely within the deliberative-process privilege. Even in the cases cited by plaintiff where sufficient need was shown to obtain discovery of police internal investigation records such evaluative data was either nonexistent or excised by the court and discovery was granted only for purely factual data in the records. Wood, supra; Frankenhauser v Rizzo, 59 FRD 339, 345 (ED Pa, 1973). In this case, while the trial court denied discovery of the internal affairs findings and analysis, the court permitted plaintiff to inquire into the area of internal affairs investigation by interrogatory or deposition. The court properly balanced plaintiff's evidentiary needs with defendant's need to keep its self-critical analyses confidential. We find no abuse of discretion.

However, we conclude that the court's denial of plaintiff's request for production of material from the personnel files of officers not involved in this litigation may have denied plaintiff access to relevant, nonprivileged material. Factual material relevant to plaintiff's claim that a constitutional violation resulted from defendant's failure to train its officers, see City of Canton, supra, could be extracted from the files by an in camera inspection similar to the court's in camera review of the personnel files of the four involved officers. The trial court abused its discretion by categorically denying discovery of the files without first conducting an in camera inspection to determine whether they contain relevant, nonprivileged material subject to discovery by plaintiff.

Finally, the records of the Humbaugh arbitration proceeding should also be subject to an in camera inspection to extract relevant factual data. It appears that the arbitration record contains witness statements and testimony regarding defendant's officers' contact with plaintiff's decedent. This testimony constitutes factual material unprotected by the deliberative-process privilege. Moreover, the eyewitness accounts and arbitration record have special evidentiary value which cannot be duplicated by deposing the arbitration witnesses, because the witnesses' recollections of the incident are no longer as fresh as at the time of the arbitration proceeding. Frankenhauser, supra, p 345. We therefore conclude that the trial court abused its discretion in failing to conduct an in camera examination of the Humbaugh arbitration record or to allow disclosure of the factual elements of the record.

Discovery rules are to be liberally construed, and materials which are not privileged and which are relevant to the subject matter of the suit are freely discoverable upon request, with no required showing of good cause. Haglund v Van Dorn Co, 169 Mich. App. 524, 529; 426 N.W.2d 690 (1988); Davis v O'Brien, 152 Mich. App. 495, 502-503; 393 N.W.2d 914 (1986). In this case, the trial court properly determined that the evaluative materials in defendant's internal affairs investigation file were privileged and thus not subject to discovery by plaintiff. However, the trial court abused its discretion in denying discovery of the Humbaugh arbitration record and departmental personnel files without conducting an in camera examination to determine whether the requested material did or did not contain unprivileged relevant material.

Affirmed in part and reversed in part.