I found this on the No2ID website.
The UK has the largest per capita DNA database in the world and the
government often stresses the infallibility of DNA evidence to justify
the expansion of the database. But now researchers at forensic DNA
technology company Nucleix say that DNA samples can be faked. They have
demonstrated how artificial DNA could be implanted into real blood
giving the blood a new profile. A modified blood sample was sent to a US
laboratory that works with FBI forensic teams and they failed to catch
the forgery. Interestingly though, Nucleix has come up with the solution
- an authentication method that distinguishes between real and fake
samples. However the mere fact that DNA can be faked may question the
reliance on DNA in criminal cases. US defence attorney Michael Cardoza
told CNN news: "it opens up an entire avenue of cross examination that
was never there before. Can you imagine their expert, the prosecution's
expert on the stand - we will now be able to ask them: 'It's possible to
fabricate DNA?'", adding "it will give a lot of defence attorneys
something to talk about in court, it will make prosecutors work a lot
harder".
Read Nucleix's research at
http://www.nucleix.com/pdf/Authentication_of_forensic_DNA_samples.pdf