On Wed, 15 Dec 2004 18:25:36 GMT, "Chip Jones"
wrote in
t::

The
problem with drugs is that you can't always know when a person is high, or
when drug use is affecting critical safety skills like judgment or
coordination.

You're probably right about detecting impaired judgment, but physical
coordination can be measured:
http://isc.temple.edu/pe204/HandCorrelationReport.htm