
89 P.3d 312 (2004)
121 Wash.App. 593
Richard SANDERS d/b/a Hotel Laminates, Appellant,
v.
Teresa WOODS and John Doe Woods, a marital community, and TNT Enterprises, a Washington Business, Respondents and Cross-Appellants.
No. 21829-5-III.
Court of Appeals of Washington, Division 3, Panel Seven.
May 6, 2004.
*313 Bruce Alan Spanner, Brandon L. Johnson, Miller, Mertens & Spanner PLLC, Kennewick, WA, for Appellant.
Floyd Edwin Ivey, Liebler Ivey Connor Berry & St. Hilaire, Attorneys at Law, Kennewick, WA, for Respondents.
SCHULTHEIS, J.
Richard Sanders, on behalf of Hotel Laminates, sued a former employee, Teresa Woods, after she started her own business, which allegedly competed directly with his business of selling advertising directories to hotels. Although Mr. Sanders filed claims for: (1) violation of the covenant not to compete; (2) misappropriation of trade secrets; (3) unfair competition in violation of the Consumer Protection Act; (4) breach of duties of trust and confidence; (5) conversion; and (6) tortious interference with contractual relationships and expectancies, the claims were dismissed on Ms. Woods' motion for summary judgment. Mr. Sanders appeals, claiming the trial court erred when it denied his motion to disqualify Ms. Woods' attorney, Floyd Ivey, based on his former representation of Mr. Sanders. He also contends the trial court erroneously granted the summary judgment motion. Ms. Woods cross-appeals, arguing the trial court erred in denying her request for attorney fees pursuant to CR 11. Because we find the trial court erred in (1) failing to disqualify Mr. Ivey, and (2) granting summary judgment, we reverse. The trial court's denial of Ms. Woods' CR 11 motion for attorney fees is affirmed.

FACTS
Mr. Sanders owns a business called Hotel Laminates, which supplies laminated advertising booklets to hotels. Teresa Woods worked for Hotel Laminates both as an independent contractor in sales and marketing, and as an employee in the position of temporary office manager. Mr. Sanders claims he requires all employees and independent contractors to sign confidentiality agreements and independent contractor agreements. Three former salespeople refute this claim. Mr. Sanders also contends Ms. Woods signed both agreements but destroyed all evidence of such after she was terminated from his employ. This statement is flatly denied by Ms. Woods.
By May 2001, Ms. Woods no longer provided independent contractor or office manager services for Hotel Laminates. Shortly thereafter, she started her own business selling advertising booklets to hotels, which, Mr. Sanders argues, competes directly with Hotel Laminates' services.
Mr. Sanders filed a lawsuit in Benton County Superior Court contending, among other things, that Ms. Woods had violated a covenant not to compete and had misappropriated trade secrets. He also successfully obtained a court order that temporarily restrained Ms. Woods from operating her business in direct competition with Hotel Laminates.
To defend her interests, Ms. Woods hired Floyd Ivey, a local patent attorney who was knowledgeable about trade secret claims. Mr. Sanders immediately objected to Mr. Ivey's representation since he had represented Mr. Sanders in the past. Mr. Sanders also claimed Mr. Ivey's business partner had professionally reviewed a noncompete agreement *314 for Mr. Sanders and Hotel Laminates in the recent past, which created a conflict of interest for Mr. Ivey. Mr. Sanders' motion to disqualify Mr. Ivey was denied after the court determined the prior representation was not substantially similar to the claim for which Ms. Woods had hired him to defend.
After discovery was underway, Ms. Woods filed a motion for summary judgment dismissal of Mr. Sanders' claims. She also filed a CR 11 motion for attorney fees, claiming the underlying suit was commenced and continued in bad faith. The court granted the summary judgment dismissal but ultimately denied the motion for attorney fees after hearing oral arguments on the matter.
On appeal, Mr. Sanders claims the trial court erred when it denied his motion to disqualify Mr. Ivey as counsel and when it granted the summary judgment dismissal. Ms. Woods cross-appeals, arguing the CR 11 motion was improperly decided.

ANALYSIS

1. Motion to Disqualify
We first determine whether the trial court erred when it denied Mr. Sanders' motion to disqualify Ms. Woods' legal counsel on the basis of conflict of interest pursuant to the Rules of Professional Conduct (RPC) 1.9. Review of a court's decision to grant or deny a motion to disqualify counsel is a legal question that is reviewed de novo. Eriks v. Denver, 118 Wash.2d 451, 457-58, 824 P.2d 1207 (1992).
RPC 1.9 provides:
A lawyer who has formerly represented a client in a matter shall not thereafter:
(a) Represent another person in the same or a substantially related matter in which that person's interests are materially adverse to the interests of the former client unless the former client consents in writing after consultation and a full disclosure of the material facts; or
(b) Use confidences or secrets relating to the representation to the disadvantage of the former client, except as rule 1.6 would permit.
In order to successfully disqualify a lawyer from representing an adversary, a former client must show that the matters currently at issue are substantially related to the subject matter of the former representation. RPC 1.9; State v. Hunsaker, 74 Wash.App. 38, 43, 873 P.2d 540 (1994). To determine whether the two representations are substantially related, we must: (1) reconstruct the scope of the facts of the former representation; (2) assume the lawyer obtained confidential information from the client about all these facts; and (3) determine whether any former factual matter is sufficiently similar to a current one that the lawyer could use the confidential information to the client's detriment. Id. at 44, 873 P.2d 540. The decision turns on whether the lawyer was so involved in the former representation that he can be said to have switched sides. Id. at 46, 873 P.2d 540. If one individual in a law firm is precluded by RPC 1.9 from representing a particular client, then all members of the firm are also prohibited from representing the client pursuant to RPC 1.10. Id. at 41-42, 873 P.2d 540.
We need not delve very deeply into the Hunsaker analysis to make our decision. The facts of this case reveal that Mr. Ivey initially represented Mr. Sanders and Hotel Laminates in a copyright and trademark infringement lawsuit commenced in the state of Oregon. Additionally, in 1997, Mr. Ivey wrote a demand letter to a former employee of Hotel Laminates, asking him to cease and desist conducting business in direct competition to Hotel Laminates. In 2000, Mr. Ivey's business partner also wrote demand letters to two former employees of Hotel Laminates. Mr. Sanders complains the substance of those letters is exactly what is at issue here. We agree.
In July 2000, Mr. Ivey's business partner sent Mr. Sanders a letter containing suggestions for contracts used by Hotel Laminates, specifically the "Noncompete and Confidentiality Clauses."[1] In that letter, counsel states he reviewed the independent contractor agreements provided by Mr. Sanders, which appeared adequate. Counsel concluded *315 the letter by offering suggestions regarding additional language that could be utilized if Mr. Sanders chose to do so.
We conclude Mr. Ivey's representation of Ms. Woods is substantially related to his previous representation of Mr. Sanders. It makes no difference whether actual confidences were disclosed to Mr. Ivey. Teja v. Saran, 68 Wash.App. 793, 799, 846 P.2d 1375 (1993). The similarities between Mr. Ivey's former representation and the current one are unmistakable. The demand letters establish this fact. The fact that some of the letters were written by Mr. Ivey's business partner is irrelevant. Hunsaker, 74 Wash. App. at 41-42, 873 P.2d 540. The most flagrant conflict is the fact that Mr. Ivey's business partner reviewed the draft of the very noncompete and confidentiality agreements that are alleged to be at issue here. The matters of the prior representation and the current one are similar and therefore substantially related. "`Substantially related' " requires only that the representations "`are relevantly interconnected or reveal the client's pattern of conduct.'" Id. at 44, 873 P.2d 540 (quoting Koch v. Koch Indus., 798 F.Supp. 1525, 1536 (D.Kan.1992)). As stated by another court: "[T]he underlying concern is the possibility, or the appearance of the possibility, that the attorney may have received confidential information during the prior representation that would be relevant to the subsequent matter in which disqualification is sought." Trone v. Smith, 621 F.2d 994, 999 (9th Cir.1980).
The facts of Mr. Ivey's former representation and the more recent representation by Mr. Ivey's business partner provide, at a minimum, the appearance of the possibility that confidential information was disclosed. The prohibition against attorneys "side switching" is based both on the RPC prohibiting the disclosure of confidences and also on the duty of loyalty the attorney owes his or her clients. Teja, 68 Wash.App. at 798-99, 846 P.2d 1375.
Mr. Ivey should have voluntarily withdrawn after Mr. Sanders timely objected to his appearance on behalf of Ms. Woods. Since he did not, the trial court should have ordered it. We reverse the trial court decision to the contrary and order the immediate disqualification of Mr. Ivey and his law firm from any further representation of Ms. Woods.

2. Summary Judgment Dismissal
The next issue presented is whether the trial court erred when it granted Ms. Woods' motion for summary judgment dismissal of the claims filed against her. We review the court's decision de novo. Folsom v. Burger King, 135 Wash.2d 658, 663, 958 P.2d 301 (1998). Summary judgment under CR 56(c) is proper only when the pleadings, affidavits, depositions, and admissions on file, viewed in the light most favorable to the nonmoving party (Mr. Sanders), show there is no genuine issue of material fact and that the moving party is entitled to judgment as a matter of law. Iwai v. State, 129 Wash.2d 84, 95-96, 915 P.2d 1089 (1996). To defeat summary judgment, Mr. Sanders' evidence must set forth specific, detailed, and disputed facts; speculation, argumentative assertions, opinions, and conclusory statements will not suffice. Suarez v. Newquist, 70 Wash.App. 827, 832, 855 P.2d 1200 (1993).
Mr. Sanders claims summary judgment was improperly granted since the record contains evidence of several genuine issues of material fact in dispute, including whether or not Ms. Woods signed a covenant not to compete and Hotel Laminates' confidentiality agreement. He says she signed them; she says she did not. Under the circumstances, a credibility determination needs to be made by a fact finder before the dispute can be resolved. The trial court erred when it made the credibility decision for the parties on summary judgment.
Mr. Sanders raises other issues for our consideration. Because his first assignment of error provides grounds for reversal of the summary judgment order, we need not reach the merits of those other issues.

3. Cross-Appeal
Regarding her cross-appeal, we find the trial court did not abuse its discretion when it denied Ms. Woods' CR 11 motion for attorney fees.


*316 CONCLUSION
Mr. Ivey and his firm are disqualified from representing Ms. Woods in this matter and the court's order denying Mr. Sanders' motion to disqualify is reversed. The summary judgment dismissal in favor of Ms. Woods is also reversed. The trial court's denial of Ms. Woods' motion for attorney fees is affirmed.
WE CONCUR: KATO, C.J., and KURTZ, J.
NOTES
[1]  Clerk's Papers at 979-81.
