On 13 Feb 2004 12:44:50 GMT someone who may be "Ian Johnston"
wrote this:-

Wel, explain in more detail, then.

Evidence can be picked up in the treads of road vehicle tyres and
shoes, then transferred to the surfaces in contact. However, that
does not mean that the police close off vast stretches of road after
a potential murder to follow the trail. The Jill Dando case is an
example. Train tyres do not have treads to pick things up and
anything microscopic that they pick up will soon be worn off.

Any evidence on the rail head will be worn off by the first train to
pass, which is usually how the potential murder scene is discovered.

No more evidence will be picked up by passing trains. They are above
the ballast and rails.

Thus covering the scene of the potential murder with plastic and
allowing the trains to run (at reduced speed) will protect the scene
and still allow services to run. When the police have excavated
themselves from the chip shop, or waited for daylight/staff, they
can do their work at a suitable time.

Note that the police cover the scene with plastic in other cases.
Also note that although you appear to not think much of plastic the
police are happy to use paper to make overalls out of.


--
David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
I will always explain revoked keys, unless the UK government
prevents me using the RIP Act 2000.