By Fiona Macrae
Using equipment found in labs up and down the country, they obliterated all traces of DNA from a blood sample and added someone else’s genetic material in its place.
The swap was so successful it fooled scientists who carry out DNA fingerprinting for U.S. courts.
The development raises the possibility of samples of blood or saliva being planted at crime scenes, leading to the innocent being wrongly convicted and the guilty going free.
Israeli researcher Dan Frumkin, who produced the bogus DNA, said: ‘If you can fake blood, saliva or any other tissue, you can engineer a crime scene. Any biology undergraduate could perform this.’
Dr Frumkin’s company, which has made a kit he claims can distinguish real DNA samples from fake ones, used two techniques to fabricate the evidence.
In the first, they extracted minute samples of genetic material from strands of hair and multiplied them many times over.
They then inserted this DNA into blood cells that had been purged of all genetic clues to their real owner.
The blood then contained the genetic fingerprint of the first person, the journal Forensic Science International: Genetics reports.
In theory, it could then be planted at the scene of a crime.
Hair, chewing gum, cigarette butts and mugs and glasses could all provide an initial DNA sample.
The company has also developed a more complicated technique, which relies on knowledge of the DNA fingerprint a ‘bar code’ of genetics from 20 set spots on a person’s DNA.
The scientists built a ‘library’ containing hundreds of DNA snippets covering all the genetic codes that crop up at the set points scrutinised by police. To make a sample matching a particular fingerprint, they just dipped into their library for the right combination and mixed them in a test-tube.
The researchers believe eventually the technology will be used by criminals.
They warned: ‘DNA evidence is key to the conviction or exoneration of suspects of various types of crime, from theft to rape and murder. However, the disturbing possibility that DNA evidence can be faked has been overlooked.
‘DNA with any desired genetic profile can be easily synthesised using common and recently developed biological techniques, integrated into human tissues or applied to surfaces of objects, and then planted in crime scenes.’
Dr John Manlove, a forensic scientist and expert witness in court cases, said: ‘Yes, it is scientifically possible but it is somebody going to an extreme.