Drunk Tests, aren't they kind of odd?

Tweet

I was watching one of those cop video shows the other night and once again they pulled someone over and gave them a drunk test. First - walk the line, he had no problem. Second - do the alphabet backward - he did that in record time. Third - touch your nose - he did fine. However the guy was way drunk as they found out eventually. Then there's me. I'm sober at this very minute and I cannot do the alphabet backward... it hurts my head! I can touch my nose, but I am tired so I might trip when I walk a line. So here's my issue... why don't they just give the breathalyzer first thing! If you suspect someone is drunk, say "here breath on this" and that's a good start. Second, what is with the backwards alphabet? A regularly sober person like me probably CAN'T do it... but a regular drunk is likely to memorize it! Same with the line and nose test, the drunks can practice that to the point that they can pass those as well. What do you think? Aren't there better ways to test drunkenness? Why don't they go straight for the breath test? And finally, can you do the alphabet backwards???