Drug Residue

The subject is "drug residue."  It is a felony offense in Virginia to possess cocaine (carries up to 10 years in prison). Of course, the law requires that the person "knowingly" and "willfully" possess the cocaine.  When we talk about residue, the issue arises as to whether the Defendant, my client, could knowingly possess cocaine if the amount is so small that it is residue.
I tried a case involving the simple possession of cocaine (I use the term "simple possession" to distinguish the situation from "possession with intent to distribute").  In order to prove the guilt of the Defendant, the Commonwealth had to show that my client "knowingly" possessed residue of cocaine present on a digital scale. Well, the chemist from the Virginia State Lab testified that she could not see any cocaine on the scale.  In order to test for it, she dipped a cotton swab in some alcohol and swabbed the scale plate with the swab.  She then tested the swab and "voila" found cocaine residue.
Accordingly, my client was found guilty of simple possession of cocaine although the presence of cocaine was not readily apparent to the naked eye.  Since he possessed a digital scale, he must be guilty.  So much for the presumption of innocence.