No statement or disclosure by the defendant concerning the alleged offense made during a competency evaluation ordered pursuant to § 19.2-169.1, a mental state at the time of the offense evaluation ordered pursuant to § 19.2-169.5, or treatment ordered pursuant to § 19.2-169.2 or § 19.2-169.6 may be used against the defendant at trial as evidence or as a basis for such evidence, except on the issue of his mental condition at the time of the offense after he raises the issue pursuant to § 19.2-168.