OPINION DENYING MOTION FOR LEAVE TO FILE APPLICATION FOR WRIT OF MANDAMUS
VANCE, Justice.In this mandamus proceeding the Relators are Betty Ann and Jack Hardesty and their attorneys of record in a case pending in the 13th District Court of Navarro County. Respondent is the Honorable Kenneth A. Douglas, Judge of that court. The Hardestys sued the real parties in interest, Medical Arts Clinic Association of Corsicana (Medical Arts) and Dr. Johann Rothwangl (“the defendants”), for medical negligence. Dr. Roth-wangl filed a motion for summary judgment supported by his own affidavit to demonstrate that he had met the appropriate standard of care in treating Betty Ann. The Hardestys filed a response to the motion, using the affidavit of Dr. Robert Capehart to controvert Dr. Rothwangl’s assertions. Medical Arts, adopting Dr. Rothwangl’s affidavit, also moved for summary judgment on the ground that its liability is contingent on Dr. Rothwangl’s liability. The court granted both motions, but we reversed the summary judgments and remanded the case for trial. Hardesty v. Rothwangl, et al., No. 10-93-169-CV (Tex.App.—Waco 1994, no writ) (not designated for publication).
After we remanded, the defendants wanted to depose Dr. Capehart. The Hardestys responded by designating him as a consulting expert under Texas Rule of Civil Procedure 166b.3.b. and refused to produce him for the deposition. The defendants filed a motion to compel the deposition and to levy sanctions for discovery abuse. The court ordered the Hardestys to produce Dr. Capehart for a deposition and awarded the defendants $4,000 in travel expenses and attorney’s fees, to be paid by the Hardestys and their attorneys within thirty days.
Relators seek to file a petition for a writ of mandamus requiring Respondent to vacate the order, asserting that Dr. Capehart’s testimony is exempted from disclosure because he has been designated as a consulting-only *550expert. See Tex.R.Civ.P. 166b.3.b. We will deny leave to file the application because, accepting their version of the facts as true, the Hardestys and their attorneys cannot demonstrate why a writ of mandamus should issue.
The identity ánd location of expert witnesses, the subject matter of their expertise, and the facts known to them are only discoverable if they are expected to testify or if their opinions or impressions have been reviewed by an expert who will testify. Id. 166b.2.e.(1). Rule 166b.3.b. further provides:
3. Exemptions. The following matters are protected from disclosure by privilege:
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b. Experts. The identity, mental impressions and opinions of an expert who has been informally consulted or of an expert who has been retained or specially employed by another party in anticipation of litigation or preparation for trial or any documents or tangible things containing such information if the expert will not be called as an expert witness, except that the identity, mental impressions and opinions of an expert who will not be called to testify as an expert and any documents or tangible things containing such impressions and opinions are discoverable if the consulting expert’s opinion or impressions have been reviewed by a testifying expert.
Id. 166b.3.b. (emphasis added). Thus, consulting-only expert witnesses enjoy special protection under the discovery rules.
The designation of an expert as a consulting-only expert may be ineffective. Tom L. Scott, Inc. v. McIlhany, 798 S.W.2d 556, 560 (Tex.1990) (orig. proceeding). In Scott, the Supreme Court held that such a designation would not preclude the remaining defendants from deposing experts who had been designated as testifying experts and who were then redesignated as consultants after the plaintiffs settled with other defendants who took an “assignment” of the experts’ testimony as part of their settlement. The Court found that the redesig-nation was, under the facts, “an offensive and unacceptable use of discovery mechanisms intended to defeat the salutary objectives of discovery.” Id. Thus, the Court held that, as a matter of law, the redesignation of the experts violated the policy underlying the rules of discovery and was therefore ineffective. Id. “[T]he protection afforded by the consulting expert privilege is intended to be only ‘a shield to prevent a litigant from taking undue advantage of his adversary’s industry and effort, not a sword to be used to thwart justice or to defeat the salutary objects’ of discovery.” Id. at 559.
In Harnischfeger Corp. v. Stone, the Fourteenth Court of Appeals determined that a plaintiff who settled with one of two defendants could not hire and redesignate as a consultant the settling defendant’s expert who had been previously designated as a testifying expert. Harnischfeger Corp. v. Stone, 814 S.W.2d 263, 265 (Tex.App.—Houston [14th Dist.] 1991, orig. proceeding) (once witness was designated as a testifying expert by settling defendant, other defendant was entitled to take his deposition). The court relied on Scott to find a violation of the policy underlying the discovery rules. Id. (citing Scott, 798 S.W.2d at 560).
The Hardestys used Dr. Capehart’s summary-judgment testimony to defeat the motions for summary judgment.1 The summary judgment rule requires the presentation of facts through affidavits rather than oral testimony. Tex.R.Civ.P. 166a(c) (“No oral testimony shall be received at the hearing.”) “A summary judgment may be based on uncon-troverted testimonial evidence of an interested witness, or of an expert witness as to subject matter concerning which the trier of fact must be guided solely by the opinion testimony of experts,....” Id. (emphasis added). The rule further requires that affidavits be made on personal knowledge, set forth facts that would be admissible in evidence at trial, and “show affirmatively that the affiant is competent to testify to the matters stated therein.” Id. at 166a(f) (em*551phasis added). Thus, in this context, the Hardestys’ filing of Dr. Capehart’s affidavit with their response to the summary judgment motion was the equivalent of calling him to testify.
We believe that the facts of this case present a stronger case for requiring the expert’s deposition than the facts of either Scott or Stone. The Hardestys have done more than designate Dr. Capehart as a testifying expert — they have actually presented his testimony in an integral part of the proceeding. Having used Dr. Capehart’s affidavit as a sword by presenting his testimony in opposition to the summary judgment, Relators cannot now use the consultant-only exemption as a shield to prevent the defendants from discovering his opinions. We find such conduct to be “an offensive and unacceptable use of discovery mechanisms intended to defeat the salutary objects of discovery.” See Scott, 798 S.W.2d at 560.
Believing that Respondent did not abuse his discretion in ordering that Dr. Capehart be produced for the defendants to take his deposition or in awarding the defendants expenses as a sanction for discovery abuse, we deny Relators’ motion for leave to file their application for writ of mandamus.
. The Hardestys' brief filed in this court in the prior proceeding asserts: “Dr. Capehart's statement ... is competent summary judgment evidence. This testimony would be admissible at trial.” (Emphasis added).