Colb on Hair

Rutgers CrimProf Sherrie Colb writes on CNN about why it is a search and/or seizure to shave the hair off a suspect, criticizing a decision of the 3d Circuit.   I really would love someone to explain to me how she could be wrong.  The 3d Circuit's view is that because hair is in plain sight, there is no reasonable expectation of privacy.  That's true as to seeing the hair, but not to cutting it off and incinerating it in a test.  My diamond ring and car are in plain sight too; does that mean the government can just take and destroy them?  [Jack Chin]