[ExI] Terrorist? Who can tell?

Lee Corbin lcorbin at rawbw.com
Tue Aug 26 02:38:17 UTC 2008

Harvey wrote

> I'm not just theorizing this.  We tried to use such a system in Florida at 
> our Bowl game a few years ago to catch wanted criminals and deadbeat dads 
> (not paying child support).  Bowl security was swamped with hundreds of 
> false positives.  They did not find a single wanted person, even though 
> there probably were some in the crowd.  They then theorized that pre-bowl 
> publicity kept criminals from going to the game.  So they deployed this in 
> Tampa's Ybor district and used it for a whole year.  Not one real 
> recognition was made.  All they got were false positives.
> Google for "Florida super bowl face recognition"
> <http://www.google.com/search?q=florida+super+bowl+face+recognition>
>> (Whereas human spotters, I presume, are not at all useless.)
> I don't have evidence for this, but anecdotally, humans were not much 
> better.  The system matched exact facial dimensions, but got gender, height, 
> weight, race, and other obvious traits wrong.  But if the criminal had 
> altered their appearance, with beard, hair color, different hair-cut, 
> glasses, etc., the computer would still match it but the human double-check 
> would likely think it was a poor match.  In general, I don't think facial 
> recognition (human or computer) works that well.

Right now, from your description, it sounds as though a human/computer
team is needed, for the purpose, say, of identifying a certain passenger
who is leaving an aircraft!

Such a pity that all the movies have it wrong about The Authorities
waiting at the end of a gang plank to apprehend someone. From now
on, they'd be well-advised to get help from some traitorous family
member, who might stand a decent chance of recognizing a husband
or other close relative, or a personal acquaintance of long standing.

>> A: "Are telling me that a row of six or more recent convicted
>> terrorist bombers could not be distinguished at the ninety-percent
>> level of confidence from a numerically similar row of Londoners
>> picked at random"  Surely you agree that I'm right about *that*,
> No, I don't agree.  As I showed with my statistical correlation, that 
> false-positives overwhelm the systems a thousand times over.  How
> would you distinguish them?  Are you saying they look different?

Yes. Now it so happens that I don't travel at all, and have
not been to London, and know of the bombings which 
occurred there only by means of my admittedly very
faulty memory, but I could have sworn that *all* those
arrested and convicted in the recent bombings were
born in the Middle East, and have the same ethnic
profiles that allow me to often recognize the origins
of people I meet. 

Hence my guess that at the 95% level of confidence,
six such individuals would be chosen as "the probable
convicts" and the other six average Londoners of the
same age and sex chosen as the "non-terrorist" group.
And only 5% of the time would the group of Londoners
picked at random---which surely includes a very wide
variety of people, nothing so nearly homogeneous
(I thought) as the bombers' group---be identified as
"the terrorists" by an ordinary set of citizens seeing each
group in a line-up.


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