
I do not think they can use the eavesdropping as evidence at all. However,
using the info they gather while listening, they can go searching THE right
place and find good, strong evidence, which they can use in court. 

Question : currently, it is easy to wire-tap, from the technical point of
view, at least. Anybody using the appropriate radio receiver can listen
to communications between a car-telephone and the ground station. The police
also, obviously. The clipper chip will make it much more difficult for the
non-authorized person to eavesdrop (note that I DO NOT write << impossible>> ).
The privacy will thus improve from the current situation. Poeple who REALLY
have something to hide already DO NOT use the phone to speak of these things.
If an illegal operation is really worth, one can afford having critical data
carried by a person rather than sending it electronically. 
The clipper chip will not change this. 

The problem is more politic. Foreign countries will never accept the clipper
chip is the access to the escrow cannot be directly granted to their own
police following their OWN law, not the US law. i.e. each country will have
its own escrow. How then will it be possible to monitor the international
traffic? or, will encrypted international traffic be possible ? or will there
be an international escrow, some kind of U.N. thing ?

Forbidding crypted communication is impractical: how is it possible to spot
a crypted communication in the thousands of megabytes of data which circulate
on the various existing networks. What about private networks ? And this will
be more and more impossible as the volume of electronic traffic will increrase
in the next years.

I think that the clipper chip can only be an interesting device to limit the
risk of , for instance, one's girlfriend's husband listening to his wife's
communications. It will bring no more as regards to security. Is it worth ?
I think so if its cost is limited, I think that many privacy invasions are done
not only by official services, but also by private entities. The clipper can
help reducing these. Provided we do not hope too much of it, it is not a real
danger and it can be helpful.