Proving innocence in a DUI case is an unusual approach, since you cannot argue that you did not ingest something that resulted in a positive DUI test. However, under certain circumstances, you may be able to use this argument in your own DUI case. Talk to your DUI attorney if any of the following apply to you.
You Are Taking a Prescribed Medication for a Major Health Condition
Interferon, which is prescribed for several serious health issues, may appear on a screen for DUIs. Other "scheduled" drugs taken for health reasons may also show up. If you can show that you are regularly taking medications for serious health conditions and that the amounts in your system are consistent with treatment doses, then your lawyer may be able to get your case thrown out. (Another possibility is that the judge will require that you find someone to drive you around rather than drive yourself, but that is unusual.)
Whoever Administers Your Medication Administration Mismanaged It
Another unusual circumstance that may apply is if you have someone else managing your medication administration. If that person mismanaged your medication administration such that you were given too much medicine, and that resulted in your DUI, that is also not your fault. Your attorney would have to prove that you do not self-administer your medication, and as such, you could not have given yourself the wrong medication or too much of it. For obvious reasons, you may need to pursue a separate lawsuit against that medication administrator, as well as fire him/her, but such actions may only bolster your "not my fault" case.
You Had an Unusual Reaction to Medication
Sometimes you can take a medication for years and not react to it, and then something changes and you do have a reaction. If your DUI is the result of a bad reaction to medicine, you can provide the courts with this documentation. You may still be required to pay for property damages or personal injuries caused by the reaction you had while driving.
However, the punishment may be reduced, and you may be able to recoup the financial losses by suing the persons, pharmacy and/or clinic that gave you the medication. Discuss your post-DUI case options with your lawyer if this particular situation applies to you. It may be very expensive to pursue, but given the nature of your case, it may also be beneficial.