In State v. Pluta, 157 Vt. 451, 600 A.2d 291, 293 (1991), the state chemist testified at trial that it is possible for a person to have a test result indicating a BAC over the legal limit with in two hours of operation and yet for that person's alcohol concentration to have actually been under the legal limit at the time of operation. The issue was whether that testimony rebutted the statutory presumption that in a civil suspension proceeding if a test result exceeding the legal limit was obtained within two hours of operation, then it shall be presumed that the defendant's alcohol concentration exceeded the legal limit at the time of operation. See 23 V.S.A. 1205(n) (formerly 1205(m)). The Court stated as follows: "To rebut a statutory presumption the opponent's evidence must do more than raise a mere theoretical possibility that the presumed fact does not exist. . . . Otherwise, the use of a presumption to shift the burden of going forward with certain evidence would be meaningless. Since a rebuttable presumption already assumes that the presumed fact will not be true in all cases, it is not rebutted simply by recognizing the possibility that it can be rebutted. To fairly put the presumed fact in issue, specific evidence is required to show that the presumed fact was not true in the particular case, given its actual underlying facts and circumstances." (Pluta, 157 Vt. at 454, 600 A.2d at 293.)