A small portion of the alcohol enters the blood stream through the lining of the mouth and then the stomach. As the contents of the stomach are emptied, the majority of the alcohol enters the blood stream through the small intestine. The alcohol gets absorbed into the system, but it is not yet uniform throughout the body.
Some time after drinking has ceased the alcohol gets fully absorbed in the bloodstream and reaches equilibrium. That means the bloods’ alcohol content is uniform throughout the body. Until that happens, any sample taken is not reliable.
The bloods’ alcohol content must be the same or uniform regardless of whether it’s located in our pinky finger or our big toe.
Pattern of drinking is crucial to this defense as it will indicate whether or not the alcohol consumed was fully absorbed.
Once alcohol is distributed in the blood stream, it will start being eliminated from the system at a somewhat constant rate of .02 per hour.