I have a case where the defense lawyer has argued to me that the very high result on his guy's blood test (.18) is the result of diabetes. From what I've read, it can affect a breath test, but I have yet to see anything where it would affect a blood test. Any insight on this would be appreciated.

It can't effect either. The machines are specific for ethanol.

The defense argument is that a diabetic who is suffering an episode of ketoacidosis will emit a fruity-sweet odor from the breath which will register as a false result on the Intoxilizer. As Jon said, the Intoxilizer is calibrated to test for only ethanol and the ketoacidosis episode is not emitting ethanol. For more information talk to your supervising technician. As a diabetic myself I know that the amount of alcohol intake to produce a 0.18 result is a major health time bomb for the diabetic in addition to the direct intoxication issues.