If I am being charged with an OWI but I wasn't behind the wheel at the time of the arrest, can I use this as part of my defense?

Yes, you can use this as part of your defense.  You are challenging the acutal physical control element of a DUI charge.  I practice in Utah so I have answered this question on many occasions.  I am sure your state has the equivalent analysis.  I have provided Utah's analysis for actual physical control, to give you an idea of what to expect.                 Utah’s DUI statute states, “A person may not operate or be in actual physical control of a vehicle within the state if the person: (a) has sufficient alcohol in the person’s body that a subsequent chemical test shows that the person has a blood or breath alcohol concentration of .08 grams or greater at the time of the test; (b) is under the influence of alcohol, any drug, or the combined influence of alcohol and any drug to a degree that renders the person incapable of safely operating a vehicle; (c) has a blood or breath alcohol concentration of .08 grams or greater at the time of operation or actual physical control.[1]                         In Utah there are several nonexclusive factors for assessing whether a person is in actual physical control of a vehicle. (the Richfield factors) They are:  (1) Whether the person was asleep or awake in the vehicle, when the peace officer discovered them; (2) Where the vehicle is positioned; (3) Whether the vehicle’s motor is running; (4) Whether the person was in the driver’s seat of the vehicle; (5) Whether the person was the sole occupant of the vehicle; (6) Whether the person possessed the ignition key; (7) The person’s apparent ability to start and move the vehicle; (8) How the vehicle got to where it was discovered; and (9) Whether the person drove the vehicle to the place it was discovered.  Utah Courts evaluate these factors under the totality of the circumstances.[2]   Hope this helps. [1] Utah Code Ann. 41-6a-502 [2] Richfield City v. Walker, 790 P.2d 87 (Utah Ct. App. 1990)