this may be splitting hairs, so to speak, and I would defer to my Florida Colleagues, but it would seem that it depends on what you are referring to, as to whether it can be used against the defendant later in the lawsuit. There is a difference between a party arguing as a whole that you did not have a contract, and he/she taking a position in a sworn affidavit as to a point of fact. For example, if a party swears in an affidavit in support of a motion to dismiss that he did this or that, and then later on at trial denies doing so, you should be able to use the earlier affidavit to impeach that party's credibility.
The defendant would be able to change his story because the motion to dismiss just attacks the compliant and is not evidence and cannot be used in summary judgment or at trial.
A motion to dismiss should be directed to the Complaint's deficiencies. The Motion should not have contained "evidence", since the judge can only look to the contents of the Complaint to see if it sets forth a proper cause of action. On a Motion to Dismiss, the judge does not rule as to the truth of its allegations, but whether the claim is properly alleged.
Unless the Motion was verified, which is to say under oath, the contents of the Motion will not be evidence. True, the jude may think it a little weird that there was a change in position, but if the defendant was not represented when the Motion was made the judge will understand that the defendant may have been educated by an attorney and now understands better what transpired.
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I agree with the other comments; motions to dismiss should not introduce evidence. However, I urge you to consider consulting with an attorney. If you're dealing with a motion to dismiss, it is best to have an attorney help you get past it. Good luck.
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