The "CSI Effect" is changing both criminals and courtrooms:

Criminals watch television too, and there is evidence they are also changing their behaviour. Most of the techniques used in crime shows are, after all, at least grounded in truth. Bleach, which destroys DNA, is now more likely to be used by murderers to cover their tracks. The wearing of gloves is more common, as is the taping shut -- rather than the DNA-laden licking -- of envelopes. Investigators comb crime scenes ever more finely for new kinds of evidence, which is creating problems with the tracking and storage of evidence, so that even as the criminals leave fewer traces of themselves behind, a backlog of cold-case evidence is building up.

The CSI effect can also be positive, however. In one case in Virginia jurors asked the judge if a cigarette butt had been tested for possible DNA matches to the defendant in a murder trial. It had, but the defence lawyers had failed to introduce the DNA test results as evidence. When they did, those results exonerated the defendant, who was acquitted.