This is from the FDNY FAQ on DNA:
On average, how long does it take to make a positive identification?
Positive identifications can only be made if a sample
from the victim was recovered (post-mortem sample)
and there is a known ante-mortem sample (such as a
fingerprint on file or dental x-ray from past dental visit).
In the case of DNA samples the required tests
may take several weeks to produce results. In the case
of non-DNA samples (fingerprint to fingerprint record)
the identification can be completed quickly.
I'm in the skeptical column.
Exactly. I mean, since we never made contact with the guy before, how are you telling me there is a DNA sample on hand to compare with? Really.
Portable DNA machines give results in one hour.
http://www.timesonline.co.uk/tol/news/uk/crime/article6723549.ece
From the UK Times.